ppm_error

TL3 Analytical chemist · Graz, AT

Wrote the mass-error checker on this site. Mass error is necessary and nowhere near sufficient.

Joined 5 October 2024 · last posted 3d · groups: analytical-chemists, wiki-editors

135 posts, newest first. Showing up to 150.

Named, unnamed and unspecified impurities as regulatory categories — the long version Replied, post #113 · Analytics › Impurities & related substances · 25 Jul 2026 · 0 likes I had read the opposite somewhere and cannot now find where, which tells me something.
Aggregate verification data across the directory, with caveats Replied, post #62 · Sourcing › Independent verification · 21 Jul 2026 · 1 like It does not extend to lots nobody has seen, it is not a recommendation, and it says nothing about anything other than what was measured. This is the sort of thing that…
Batch numbers that do not match the vial label Replied, post #46 · Sourcing › Red flags · 20 Jul 2026 · 8 likes Post #45 answers the question as asked. The question underneath it is different. The reason batch numbers keeps being re-asked is that the answer is conditional and…
Journal club: SUSTAIN 6 and its retinopathy signal Replied, post #79 · Evidence › Journal club · 18 Jul 2026 · 23 likes Where the group cannot agree, record the disagreement rather than resolving it by seniority. The recorded disagreement is more honest and more useful later. That is a…
Follow-up: How compounding permissions changed when supply normalised Replied, post #33 · Sourcing › Regulatory · 17 Jul 2026 · 0 likes The arithmetic in post #32 is right; the assumption feeding it is the part to check. Answering the compounding permissions question as asked, then the question I think…
Why we ask for units every single time, with three examples of what goes wrong Replied, post #129 · Start Here › How to Ask · 14 Jul 2026 · 0 likes Where I part company with post #127, and it is a narrow parting. Disagreeing with an answer you got: cite what you disagree with, say what contradicts it, and ask which…
What a reversed-phase purity number actually is Replied, post #40 · Analytics › HPLC & UHPLC · 10 Jul 2026 · 7 likes On post #36 — agreed on the reasoning, with one qualification. Practical answer on reversed-phase purity number, since the theoretical one is upthread: do the simplest…
Journal club: indirect comparison between two programmes, defended and attacked Replied, post #111 · Evidence › Journal club · 8 Jul 2026 · 8 likes Post #108 put the caveat in the right place and I want to underline it. My experience of indirect comparison contradicts the reply above. I am posting it as a data…
Follow-up: The retatrutide phase 2 obesity paper, read closely Replied, post #20 · Compounds › Retatrutide · 30 Jun 2026 · 8 likes What we do not know about retatrutide, listed explicitly: long-term safety, real-world response rates, the dose response in diverse populations, whether the heart-rate…
A single out-of-range value on an otherwise normal panel Replied, post #61 · Clinical › Bloodwork · 18 Jun 2026 · 0 likes Adding a small correction to the single out-of-range value summary above rather than a disagreement with it. The substance holds; one of the figures is out by a factor…
Micronutrient adequacy at low total intake Replied, post #87 · Nutrition & Training › Protein & intake · 13 Jun 2026 · 15 likes I read post #85 twice before replying, because I had assumed the opposite. The strongest argument against my own position on micronutrient adequacy, stated as well as I…
A parcel stationary at a customs facility for nine days Replied, post #68 · Sourcing › Logistics · 7 Jun 2026 · 27 likes Packaging integrity on arrival: if a parcel arrives with compromised packaging, that is evidence of a handling problem in transit. The contents may or may not be…
A reconstituted vial's beyond-use date and the reasoning behind common figures Replied, post #55 · Practice › Storage & stability · 5 Jun 2026 · 18 likes An observation about reconstituted that I cannot explain and am posting anyway, on the principle that unexplained observations are more useful public than private.
Rewriting my first post: a before-and-after, with commentary — what changed since Replied, post #5 · Start Here › How to Ask · 5 Jun 2026 · 31 likes I came in to disagree and I am leaving without a disagreement.
An appeal that succeeded, with the letter structure — the long version Replied, post #38 · Access › Insurance & coverage · 1 Jun 2026 · 0 likes Reframing appeal slightly, because I think the disagreement is about the question rather than the answer. If the question is "does it happen", yes. If it is "how…
Second pass at: Metformin co-administration and additive GI effects Replied, post #114 · Practice › Interactions · 28 May 2026 · 22 likes A supplement is a drug for interaction purposes, and the fact that it is sold without a prescription tells you nothing about whether it interacts. The paperwork is…
Personal import allowances, compared — a second dataset Replied, post #130 · Access › International · 25 May 2026 · 0 likes Post #126 put the caveat in the right place and I want to underline it. Import rules for personal use: what you can import for personal use depends on your country's…
Official shortage notices and what they authorise Replied, post #60 · Access › Shortages · 20 May 2026 · 1 like This follows post #57 rather than contradicting it. Shortage predictions: regulators and suppliers issue shortage alerts before they become acute. Checking the…
Injection volume, overload, and peak distortion Replied, post #14 · Analytics › HPLC & UHPLC · 20 May 2026 · 6 likes Injection volume is one of those subjects where the general answer and the answer for a specific case diverge, and the thread will go in circles until someone says…
Follow-up: Search filters: what is missing Replied, post #106 · Meta › Site feedback · 19 May 2026 · 25 likes Taking post #103 at face value and following it one step further. If you are new and reading this thread for the answer to Search filters: the answer is conditional,…
Coming back to: Why a preprint's supplementary material is often the best part Replied, post #52 · Evidence › Preprints · 13 May 2026 · 0 likes The honest position on most preprints in this field is that they are interesting and provisional, and that saying both is not fence-sitting. If anyone has run this…
Two scans six weeks apart on different machines: a cautionary tale Replied, post #16 · Outcomes › Body composition · 11 May 2026 · 2 likes Post #15 answers the question as asked. The question underneath it is different. Absolute lean mass and lean mass as a proportion move differently and answer different…
A calculator that gives a right answer to the wrong question Replied, post #20 · Data & Tools › Calculators · 9 May 2026 · 0 likes Post #17 is the version of this I will quote in future. One addition. The residual-volume question belongs in the tool rather than in a footnote, because it is the…
Request: show the solution author in the topic list — what changed since Replied, post #13 · Meta › Feature requests · 30 Apr 2026 · 4 likes Request from the analytics side: allow a table in a post to be marked as data rather than layout, so it can be copied without the formatting. Half the tables here are…
Converting between mg/mL and units per dose, both directions — the long version Replied, post #79 · Practice › Reconstitution · 23 Apr 2026 · 0 likes Choosing a concentration on purpose rather than by accident: starting with "I want to draw 0.5 mL per dose" and working backward to the required concentration is more…
Run-in periods and the population they select Replied, post #104 · Evidence › Trials · 22 Apr 2026 · 0 likes Post #103 is right about the mechanism and I think understates the practical bit. Risk of bias: structured appraisal of internal validity. Key things to assess:…
Pre-registering a personal experiment, seriously — a second dataset Replied, post #59 · Research Methods › N-of-1 designs · 22 Apr 2026 · 0 likes I changed my mind about Pre-registering a personal experiment after someone here asked me for the source and I could not produce one. That is worth saying out loud…
Joined after a search result and stayed Replied, post #3 · Lounge › Introductions · 22 Apr 2026 · 32 likes Clinician voices are genuinely welcome and are asked to be explicit about the line. Several members here say plainly in every post that they are describing general…
Measurement error in home scales, with a worked standard deviation — the long version Replied, post #84 · Research Methods › Statistics · 21 Apr 2026 · 0 likes Answering the question post #80 raises rather than the one it answers. A p-value is the probability of data at least this extreme given the null hypothesis. It is not…
Prescription requirements and telehealth models — a second dataset Replied, post #6 · Sourcing › Regulatory · 18 Apr 2026 · 7 likes I had written a reply contradicting post #4 and deleted it. Here is what survived. Reframing Prescription requirements and telehealth models slightly, because I think…
Blind submission and why it changes minds — the long version Replied, post #22 · Sourcing › Independent verification · 13 Apr 2026 · 7 likes Coming back to post #20, because the follow-up matters more than the original answer. Repeat testing: if you want to verify the same lot a second time, testing with a…
Spike-and-recover accuracy for a peptide assay Replied, post #100 · Analytics › Method validation · 10 Apr 2026 · 1 like Confirming post #97 from a second method, which matters more than confirming it from a second person. Limits of detection and quantitation: LOD is the lowest…
GLP-1 receptor distribution: central and peripheral Replied, post #29 · Pharmacology › Receptor biology · 9 Apr 2026 · 0 likes GLP-1 receptor signalling: the GLP-1 receptor is expressed on beta cells (insulin secretion), on neurons (appetite and gastric motility), and on myocardium…
Prediction intervals and why they are more honest than confidence intervals Replied, post #15 · Evidence › Meta-analyses · 6 Apr 2026 · 31 likes Careful with the language on prediction intervals. "Not detected" and "not present" are different findings and the first is a statement about the method.
A checklist for reading a certificate in under two minutes Replied, post #2 · Analytics › COA interpretation · 5 Apr 2026 · 17 likes "Not less than 98 per cent" is a specification. "98.3 per cent" is a result. A certificate carrying only the first has not told you what was measured. It is worth…
[2026 update] Charge states for a 4 kDa peptide, worked through Replied, post #17 · Analytics › Mass spectrometry · 19 Mar 2026 · 16 likes I read post #16 twice before replying, because I had assumed the opposite. Electrospray ionisation produces multiply charged ions. For a 4 kDa peptide you expect mostly…
Type 2 diabetes and the largest part of the evidence base Replied, post #31 · Clinical › Comorbidities · 15 Mar 2026 · 1 like The thing about type 2 diabetes that took me longest to accept is that a plausible mechanism is not evidence of an effect. It is a reason to look, not a result.
[2026 update] What a purity-only report leaves out Replied, post #53 · Sourcing › Independent verification · 14 Mar 2026 · 15 likes This follows post #52 rather than contradicting it. Repeat testing: if you want to verify the same lot a second time, testing with a different service strengthens the…
Angle of injection and whether 90 degrees is always right Replied, post #116 · Practice › Administration · 14 Mar 2026 · 0 likes Pinching a fold is useful for lean tissue and unnecessary elsewhere. The point is to keep the needle out of muscle, and whether you need to depends on the site and on…
Micro-titration: a disputed topic, argued properly — one year on Replied, post #13 · Practice › Dosing & titration · 13 Mar 2026 · 33 likes The four-week step is a trial convention, not a pharmacological constant. It is roughly four half-lives for a week-long half-life, which is the interval at which you…
A parcel stationary at a customs facility for nine days Replied, post #37 · Sourcing › Logistics · 11 Mar 2026 · 13 likes Two sentences on parcel stationary and then I will stop, because the rest is speculation and the thread is better without mine. What is documented is narrow. What is…
The lowest dose that does anything: is that a real question? Replied, post #45 · Practice › Dosing & titration · 4 Mar 2026 · 24 likes The strongest argument against my own position on lowest dose, stated as well as I can state it, since nobody else has yet.
Molecular mass of semaglutide and why the figure differs between sources Replied, post #13 · Compounds › Semaglutide · 4 Mar 2026 · 0 likes Acknowledging rather than arguing. The reasoning holds as far as I can follow it.
Reconstitution volumes that produce round numbers, tabulated Replied, post #57 · Practice › Reconstitution · 2 Mar 2026 · 29 likes Second-hand on reconstitution volumes, so weight it accordingly — someone whose method I trust told me this and I have not verified it myself.
Grapefruit: why this class is not the class that cares Started this topic · Practice › Interactions · 27 Feb 2026 · 45 likes Grapefruit: why this class is not the class that cares Writing it up because I had to work it out twice and would rather nobody else did. I was wrong about grapefruit…
Revisiting: The report format the maintainers ask for, and why each field is there Replied, post #26 · Sourcing › Vendor reports · 22 Feb 2026 · 12 likes Dosing and purity: a vial that is 99% pure might contain 80% of its label claim if the other mass is water, counter-ion, and excipient. Purity and content are…
[2026 update] A rising related-substance total over six months: degradation or method… Replied, post #66 · Analytics › Impurities & related substances · 19 Feb 2026 · 0 likes Related substances: compounds chemically related to the target peptide but not the target peptide itself. The standard method separates them and reports them as area…
[2026 update] A rising related-substance total over six months: degradation or method… Replied, post #13 · Analytics › Impurities & related substances · 10 Feb 2026 · 22 likes Trifluoroacetate is a counter-ion rather than an impurity, and it appears in the mass balance rather than in the chromatogram. Conflating the two accounts for several…
Follow-up: A supplier that answers analytical questions with restated claims Replied, post #78 · Sourcing › Red flags · 5 Feb 2026 · 0 likes Exaggerated claims without documentation: every compound has limits. No peptide is "100% pure" because purity is measured to finite precision. A supplier claiming…
Micro-titration: a disputed topic, argued properly Replied, post #30 · Practice › Dosing & titration · 3 Feb 2026 · 28 likes The four-week escalation interval is a convention from the pivotal trials, not a pharmacological constant. The pharmacological argument is that with a week-long…
[2026 update] Does a peptide degrade silently, with no visual change? Replied, post #19 · Practice › Storage & stability · 1 Feb 2026 · 7 likes An observation about peptide that I cannot explain and am posting anyway, on the principle that unexplained observations are more useful public than private.
Interpreting a result that disagrees with the supplier's certificate Replied, post #101 · Sourcing › Independent verification · 30 Jan 2026 · 10 likes Post #100 is the version of this I will quote in future. One addition. The practical version of interpreting a result is three sentences long. The rigorous version is…
Follow-up: A supplier that answers analytical questions with restated claims Replied, post #45 · Sourcing › Red flags · 10 Jan 2026 · 4 likes Something worth flagging about supplier: the strongest-sounding claims in this thread are the ones with no source attached, which is the usual pattern and not a…
Stepping down deliberately, and how to do it without losing progress Replied, post #40 · Practice › Dosing & titration · 10 Jan 2026 · 28 likes Everything in post #37 holds. The case it does not cover is the one I have. Concentration and dose get conflated constantly in this subcategory. Changing how much…
Run-in periods and the population they select Replied, post #45 · Evidence › Trials · 4 Jan 2026 · 17 likes Absolute numbers, not just relative: a 30% relative reduction tells you the ratio but not the practical magnitude. The event rate in each arm and the difference between…
Whether protein timing matters at a large deficit Replied, post #12 · Nutrition & Training › Protein & intake · 28 Dec 2025 · 8 likes Seconded. It reads as careful rather than confident, which is the right register.
Journal club: the retatrutide phase 2 obesity paper Replied, post #11 · Evidence › Journal club · 14 Dec 2025 · 0 likes Somebody should be asked to argue the paper's case even if nobody in the room believes it. Sessions where everyone agrees produce a summary nobody can use. Worth one…
Why the titration planner refuses to produce a schedule below a floor Replied, post #15 · Data & Tools › Calculators · 3 Dec 2025 · 28 likes I have no financial interest in anything named in this thread and I want to say so before I comment on titration planner refuses, because it is the sort of subject…
How to read a forest plot, properly, from scratch Replied, post #64 · Evidence › Trials · 2 Dec 2025 · 6 likes Risk of bias: structured appraisal of internal validity. Key things to assess: randomisation method (was it truly random or could someone predict the next assignment),…
Pooling trials with different estimands — what changed since Replied, post #58 · Evidence › Meta-analyses · 29 Nov 2025 · 8 likes A meta-analysis of four small trials is not stronger evidence than one adequately powered trial, whatever the summary statistic looks like.
Tirzepatide's shorter half-life and its one practical consequence Replied, post #16 · Compounds › Tirzepatide · 29 Nov 2025 · 9 likes This follows post #15 rather than contradicting it. The 2.5 mg starting dose is a tolerance step and not a therapeutic one. Judging efficacy at that dose is the single…
DXA precision and the least significant change for lean mass Replied, post #29 · Outcomes › Body composition · 29 Nov 2025 · 0 likes Preserving lean tissue during a substantial deficit depends on protein intake and a resistance stimulus, and the evidence for both is reasonably strong. Old habit: I…
Second pass at: Programming during a large energy deficit Replied, post #91 · Nutrition & Training › Resistance training · 21 Nov 2025 · 7 likes No notes. Posting so the count is not one.
Lurking for two months before posting: was that the right call? Replied, post #9 · Start Here › Welcome · 17 Nov 2025 · 3 likes Reading the guidelines before you post is genuinely worth the twenty minutes. Not because you will break one, but because the rules explain why the place reads the way…
Dead volume across syringe and needle combinations Replied, post #25 · Devices › Syringes & needles · 17 Nov 2025 · 0 likes Dead volume: residual liquid in the hub and needle after withdrawal. Typical residual is 0.01 to 0.02 mL for an insulin syringe with a fixed needle. Accounting for it…
Revisiting: Aggregates and why a purity assay may miss them entirely Replied, post #7 · Analytics › Impurities & related substances · 13 Nov 2025 · 14 likes The arithmetic in post #4 is right; the assumption feeding it is the part to check. A supplier that can tell you what its principal impurity is has answered a harder…
A history of disordered eating: proceeding carefully Replied, post #3 · Wellbeing › Mental health · 11 Nov 2025 · 2 likes On the opening post — agreed on the reasoning, with one qualification. The social side of this — how other people respond to visible change — comes up constantly and…
[2026 update] What steady state means for the decision to escalate Replied, post #39 · Practice › Dosing & titration · 9 Nov 2025 · 18 likes The arithmetic in post #38 is right; the assumption feeding it is the part to check. Steady state came up in a thread eighteen months ago and was answered well. I…
[2026 update] What steady state means for the decision to escalate Replied, post #7 · Practice › Dosing & titration · 4 Nov 2025 · 0 likes Steady state means the plasma concentration is stable from dose to dose. That happens around 4 to 5 half-lives. Before that, the concentration is rising with each dose.…
A 40-week log with the measurement method stated Replied, post #42 · Outcomes › Progress reports · 20 Oct 2025 · 28 likes Post #41 put the caveat in the right place and I want to underline it. Menstrual cycle: for people who menstruate, weight can shift by several pounds across the cycle…
Why an oral GLP-1 agonist is a formulation achievement more than a chemistry one Replied, post #11 · Compounds › Oral incretins · 20 Oct 2025 · 2 likes Timing consistency matters more for oral dosing than for weekly injection, because absorption depends on the state of the stomach and the state of the stomach varies…
A preprint whose numbers changed substantially at publication Replied, post #95 · Evidence › Preprints · 17 Oct 2025 · 12 likes Post #92 is right about the mechanism and I think understates the practical bit. Unrefereed work is not worthless and a great deal of it survives review substantially…
Compounds this community declines to help with, and why Replied, post #71 · Compounds › Other compounds · 6 Oct 2025 · 11 likes Right — I had this wrong and I am glad to have read it before it mattered.
What a 2 ppm match establishes, and what it does not Replied, post #52 · Analytics › Mass spectrometry · 19 Sep 2025 · 2 likes Fair, and the limits you put on it are the part I will remember.
Temperature loggers worth the money — the long version Replied, post #42 · Devices › Cold chain · 18 Sep 2025 · 0 likes Post #40 describes the usual case. This is about the unusual one. The number people quote for Temperature loggers worth the money is a central estimate presented…
How to read a forest plot, properly, from scratch Replied, post #28 · Evidence › Trials · 15 Sep 2025 · 3 likes Narrowing post #27, because the general version has more than one answer. Risk of bias: structured appraisal of internal validity. Key things to assess: randomisation…
Reverse causation in a cohort study of weight and outcome — a second dataset Replied, post #10 · Evidence › Study critique · 12 Sep 2025 · 8 likes Per-protocol and intention-to-treat analyses answer different questions and neither is the honest one by default. Reporting both is the practice worth insisting on.
The most useful thing you learned here that was not the answer you came for — a second… Replied, post #24 · Lounge › Off topic · 7 Sep 2025 · 24 likes Lounge-level thought to close on: the measure of this place is that being wrong in public here is cheap. That is a design decision and it took work. Not the answer, but…
Second pass at: Why this subcategory is stricter about sourcing than most Replied, post #125 · Compounds › Secretagogues & GH axis · 2 Sep 2025 · 0 likes Storage: these are lyophilised short peptides and are generally reasonably stable dry and considerably less so in solution. Reconstituting only what will be used within…
Second pass at: The mass-error checker and its intended scope Replied, post #6 · Data & Tools › Calculators · 26 Aug 2025 · 12 likes The reason mass-error checker is hard to answer is that the obvious measurement and the relevant quantity are not the same thing, and substituting one for the other is…
Managing an unplanned gap in supply — what changed since Replied, post #41 · Access › Shortages · 18 Aug 2025 · 0 likes International supply chains: a shortage in one country does not mean shortage in another. That is why ordering from multiple suppliers before a shortage gets bad is…
A ten-fold dose error caught before injection — one year on Replied, post #93 · Devices › Syringes & needles · 3 Aug 2025 · 16 likes Marking my uncertainty on ten-fold dose error caught explicitly. I am confident about the direction, much less confident about the size, and not confident at all that…
Coming back to: Sample size calculations, read backwards from the published number Replied, post #66 · Evidence › Trials · 1 Aug 2025 · 1 like That matches what I have seen, for whatever a single anecdote is worth.
Temperature loggers worth the money — the long version Replied, post #15 · Devices › Cold chain · 23 Jul 2025 · 26 likes If you are not going to be there, arranging a secure delivery point is worth more than any packing decision the supplier can make. I would rather say I do not know than…
What a documentation review can and cannot tell you Replied, post #40 · Sourcing › Independent verification · 19 Jul 2025 · 0 likes Post #39 is right about the mechanism and I think understates the practical bit. VendorInvestigate: documentation and supplier-practice review. Reviews paperwork rather…
Why oral semaglutide needs an absorption enhancer at all Replied, post #19 · Compounds › Oral incretins · 17 Jul 2025 · 10 likes The absorption enhancer in the licensed oral product works by transiently raising local gastric pH and promoting absorption across the mucosa. It is the reason the…
A field-by-field walk through a certificate of analysis Replied, post #36 · Analytics › COA interpretation · 15 Jul 2025 · 19 likes Narrowing post #34, because the general version has more than one answer. Field-by-field walk through a certificate is one of those subjects where the general answer…
Journal club: the CagriSema phase 2 combination paper — a second dataset Replied, post #68 · Evidence › Journal club · 5 Jul 2025 · 5 likes Suggest the next paper at the end of the session rather than by message afterwards. The room has just worked out what it wants to know next.
Reading a chromatogram someone posted without axes Replied, post #54 · Analytics › HPLC & UHPLC · 4 Jul 2025 · 6 likes Answering the question post #50 raises rather than the one it answers. Purity by chromatography answers "what proportion of what I detected is the intended species". It…
What this community means by "a source", in practical terms Replied, post #18 · Start Here › Welcome · 28 Jun 2025 · 5 likes Nothing to add on the substance. Thank you for taking the question at face value.
Request: a diff view for wiki revisions — the long version Replied, post #11 · Meta › Feature requests · 20 Jun 2025 · 32 likes Community support: if other people support your request, they can reply with "+1" or "I would use that too". Widely-requested features are prioritised. I would not lead…
Whether an aggregate is worth publishing at all: a disputed topic Started this topic · Data & Tools › Datasets · 10 Jun 2025 · 1 like On the subject in the title: Whether an aggregate is worth publishing at all: a disputed topic Working notes rather than a conclusion. An honest uncertainty about…
The CagriSema phase 2 paper and what a fixed combination buys — the long version Replied, post #37 · Compounds › Cagrilintide & amylin analogues · 7 Jun 2025 · 0 likes Taking post #36 at face value and following it one step further. I keep a log for CagriSema phase 2 paper specifically because my memory of it turned out to be…
Second pass at: Triple agonism: additive, synergistic, or neither? Replied, post #61 · Compounds › Retatrutide · 7 Jun 2025 · 0 likes Heart rate increased in a dose-dependent way in the phase 2 work. That is not a footnote — it is one of the specific things phase 3 exists to characterise, and it is…
Coming back to: Getting a referral rather than a refusal Replied, post #24 · Clinical › Prescriber conversations · 2 Jun 2025 · 0 likes Following, with nothing to contribute beyond having asked the same thing elsewhere.
Follow-up: The lowest dose that does anything: is that a real question? Replied, post #15 · Practice › Dosing & titration · 22 May 2025 · 28 likes A missed dose in a weekly schedule is not a trough to chase. With a week-long half-life you are perturbing a slowly moving average, and the labelling for licensed…
Adjudicated events and why the definition matters — the long version Replied, post #146 · Evidence › Trials · 10 May 2025 · 2 likes Surrogate endpoints: an endpoint that is not the outcome that matters but is measured as a stand-in. HbA1c is a surrogate for long-term glucose control and the…
Comparators chosen for regulatory reasons rather than clinical ones Started this topic · Evidence › Trials · 9 May 2025 · 29 likes On the subject in the title: Comparators chosen for regulatory reasons rather than clinical ones Working notes rather than a conclusion. An honest uncertainty about…
Obstructive sleep apnoea and a hard endpoint in this class Replied, post #72 · Clinical › Comorbidities · 30 Apr 2025 · 11 likes Chronic kidney disease: compounds in this class have renal benefit in people with kidney disease. The benefit appears to be additive to other renal-protective agents,…
Delayed gastric emptying and oral medication absorption: which drugs matter Replied, post #32 · Practice › Interactions · 31 Mar 2025 · 8 likes Second-hand on delayed gastric emptying and oral, so weight it accordingly — someone whose method I trust told me this and I have not verified it myself.
About the Body composition category Replied, post #4 · Outcomes › Body composition · 25 Mar 2025 · 0 likes Suggestion for the wiki post above: it would be worth linking the two or three most-referenced topics in this category directly, since new members reliably ask for…
Tirzepatide in type 2 diabetes: the SURPASS programme, summarised honestly Replied, post #41 · Compounds › Tirzepatide · 17 Mar 2025 · 9 likes Grateful for the specificity. Vague answers to this question are what sent me looking.
Adjudicated events and why the definition matters — the long version Replied, post #38 · Evidence › Trials · 8 Mar 2025 · 17 likes This is the first time the answer has come with its own limits attached. Appreciated.
Journal club: SURMOUNT-OSA and a hard endpoint in a soft field Replied, post #13 · Evidence › Journal club · 26 Feb 2025 · 17 likes Distinguishing three things in the SURMOUNT-OSA discussion that keep getting used interchangeably: the observation, the proposed mechanism, and the recommendation that…
Research-use-only labelling: what it means and what it does not — the long version Replied, post #79 · Sourcing › Regulatory · 6 Feb 2025 · 6 likes I had written a reply contradicting post #75 and deleted it. Here is what survived. Small methodological point on Research-use-only labelling: repeating a measurement…
Second pass at: Cross-border purchase within the EU: the actual rules Replied, post #30 · Access › International · 6 Feb 2025 · 0 likes Country-by-country legality: compound approval and legal status differ substantially by jurisdiction. Semaglutide approved in the United States and European Union;…
What the published dose-response for semaglutide actually looks like above 2.4 mg — a… Replied, post #51 · Compounds › Semaglutide · 4 Feb 2025 · 1 like Counter-ion form matters for the arithmetic and is almost never stated. A vial labelled 5 mg of peptide as an acetate salt and one labelled 5 mg as trifluoroacetate do…
Second pass at: Gauge and length selection for subcutaneous injection Replied, post #24 · Devices › Syringes & needles · 28 Jan 2025 · 0 likes U-100 means the barrel is graduated for a solution containing one hundred units of insulin per millilitre. For anything that is not insulin, the units are simply…
Why mass spectrometry cannot tell you about an epimer Replied, post #30 · Analytics › Mass spectrometry · 17 Jan 2025 · 10 likes Fair, and the limits you put on it are the part I will remember.
[2026 update] Lipid changes during rapid weight loss: the expected trajectory Replied, post #13 · Clinical › Bloodwork · 9 Jan 2025 · 16 likes This follows post #10 rather than contradicting it. Small correction to my own earlier position on Lipid changes during rapid weight. I had the units the wrong way…
What changed in 2026, by region Replied, post #61 · Access › International · 6 Jan 2025 · 1 like Both are useful and they are different contributions. A first-hand account and a citation answer different halves of the question.
Body image changing more slowly than the body Replied, post #120 · Wellbeing › Mental health · 24 Dec 2024 · 0 likes Expectations set by other people's reported trajectories are a documented source of distress, and the trajectories posted are not representative. That is my reading.…
Second pass at: Choosing a concentration on purpose rather than by accident Replied, post #37 · Practice › Reconstitution · 5 Dec 2024 · 0 likes Over-dilution: if your target dose is 0.25 mg and your syringe is a 1 mL insulin syringe, you need a concentration high enough that 0.25 mg fits on the scale. A 0.25…
Coming back to: Preparing for an appointment: one page, three questions Replied, post #115 · Clinical › Prescriber conversations · 5 Dec 2024 · 30 likes Post #112 answers the question as asked. The question underneath it is different. A question phrased as "what would you want to see before considering X" is answerable…
Pancreatitis history and the risk calculus — a second dataset Replied, post #15 · Safety › Contraindications · 2 Dec 2024 · 4 likes Understood, and I withdraw the assumption I opened with.
Converting between mg/mL and units per dose, both directions Replied, post #109 · Practice › Reconstitution · 29 Nov 2024 · 17 likes Worth separating two things that post #106 runs together. Two people can reconstitute the same vial to different concentrations and both be right. The dose is the same;…
Revisiting: Moderation log format change Replied, post #39 · Meta › Announcements · 23 Nov 2024 · 2 likes That is a fair summary of where the discussion has got to.
Revisiting: Melanocortin agonists: mechanism and the documented adverse profile Replied, post #124 · Compounds › Other compounds · 18 Nov 2024 · 29 likes Thymosin alpha-1 has a regulatory history in several jurisdictions and a real clinical literature, which puts it in a different evidential category from most of its…
Reading a preclinical wound-healing model and its relevance to a human tendon Replied, post #20 · Compounds › Repair & healing peptides · 9 Nov 2024 · 14 likes Post #19 is right about the mechanism and I think understates the practical bit. The practical version of reading a preclinical wound-healing model is three sentences…
Follow-up: Where the four-week escalation interval comes from, and what it is not Replied, post #96 · Practice › Dosing & titration · 3 Nov 2024 · 11 likes Worth separating two things that post #92 runs together. Four-week escalation interval would be much easier to settle if anyone reported the denominator. Almost nobody…
A side-effect grading scheme this community uses, and its limits — the long version Replied, post #2 · Practice › Side effects · 29 Oct 2024 · 0 likes The useful distinction on side-effect grading scheme is between what was measured and what was inferred from it. Both end up in the same sentence and only one of them…
Choosing which test to pay for, given a fixed budget — does this still hold? Replied, post #4 · Sourcing › Independent verification · 20 Oct 2024 · 17 likes It does not extend to lots nobody has seen, it is not a recommendation, and it says nothing about anything other than what was measured.
Follow-up: A site rotation scheme that is easy enough to actually follow Replied, post #82 · Practice › Administration · 5 Oct 2024 · 0 likes Leaving the needle in for a couple of seconds after depressing the plunger reduces leakage at the site. It costs nothing and it is the fix for the "some came back out"…
Revisiting: Melanocortin agonists: mechanism and the documented adverse profile Replied, post #9 · Compounds › Other compounds · 19 Sep 2024 · 25 likes Practical answer on Melanocortin agonists, since the theoretical one is upthread: do the simplest check first, write down the result, and only then decide whether the…
Follow-up: Dead volume across syringe and needle combinations Replied, post #35 · Devices › Syringes & needles · 15 Sep 2024 · 25 likes For anyone finding this later: the short answer on Dead volume across syringe is that it depends on one thing, and the rest of the thread is people identifying which…
Second pass at: Sodium, potassium and magnesium when intake drops Replied, post #48 · Nutrition & Training › Hydration & electrolytes · 19 Aug 2024 · 0 likes The very ordinary causes of week-two malaise: inadequate hydration, low sodium intake, too-rapid calorie deficit, and inadequate sleep are more common causes of fatigue…
High-resolution MS on aggregates and what it can see — one year on Replied, post #18 · Analytics › Mass spectrometry · 13 Aug 2024 · 0 likes Electrospray on a peptide of this size gives a multiply charged series rather than a single ion. Seeing only one charge state usually means the deconvolution has…
Reporting a discrepancy without making an allegation Replied, post #6 · Sourcing › Vendor reports · 27 Jul 2024 · 0 likes What I would want before treating reporting a discrepancy as settled: the method, the sample, and whether anyone tried to find the opposite result. Two of the three are…
Second pass at: Retatrutide dose escalation in the published trials Replied, post #47 · Compounds › Retatrutide · 19 Jul 2024 · 1 like Comparisons with tirzepatide are being made across trials rather than within one. Different populations, different durations, different endpoints; the effect sizes are…
Promotion criteria, and the one that stops most nominations Replied, post #19 · Documentation › Doc review · 16 Jul 2024 · 12 likes I will take the caveat as seriously as the claim, which is the point of putting it there.
Cold packs, phase-change material, and what survives ten days Replied, post #91 · Sourcing › Logistics · 10 Jul 2024 · 1 like Picking up post #88: that is the part I would want checked first. The version of cold packs that circulates here is a simplification of a simplification. It is not…
Splitting a weekly dose in two: the pharmacokinetic argument against — the long version Replied, post #128 · Practice › Dosing & titration · 10 Jul 2024 · 22 likes Dose equivalence between different incretin analogues is a weak concept. The molecules differ in structure, half-life, receptor selectivity, and in what has been…
Oral contraceptives and delayed emptying: what the data shows Replied, post #6 · Practice › Interactions · 5 Jul 2024 · 0 likes Where the oral contraceptives and delayed emptying discussion usually stalls is that nobody wants to say "I do not know" and everyone is willing to say "it varies".…
Follow-up: Oral contraceptives and delayed emptying: what the data shows Replied, post #2 · Practice › Interactions · 8 Jun 2024 · 0 likes What I would tell a new member reading about Oral contraceptives and delayed emptying for the first time: the confident posts are not the reliable ones, and the…
Assessing a warm arrival: the decision process — one year on Replied, post #55 · Sourcing › Logistics · 30 May 2024 · 1 like Split shipments reduce single-point risk and increase the number of transits. Which trade is right depends on what you are protecting against. Worth reading the earlier…