k.perrin

TL2 · Galway

Contributes reviews on supplier material. Based in Galway.

Joined 7 December 2024 · last posted 2d

84 posts, newest first. Showing up to 150.

Primary endpoint hierarchies and why order matters — one year on Replied, post #60 · Evidence › Trials · 26 Jul 2026 · 0 likes Dropout is information: high dropout rates can indicate tolerability problems or lower efficacy than the summary suggests. Where the analysis handled dropouts matters.…
Submitting a sample: the process end to end Replied, post #87 · Sourcing › Independent verification · 16 Jul 2026 · 4 likes The arithmetic in post #86 is right; the assumption feeding it is the part to check. Checked the submitting a sample claim against the primary source this morning. It…
Why we ask for units every single time, with three examples of what goes wrong Replied, post #132 · Start Here › How to Ask · 15 Jul 2026 · 6 likes Timeline questions need the timeline. Dates, in order, with what happened on each. "A while ago" and "recently" are the two least useful words in a question of this…
Osteoarthritis and mechanical versus metabolic improvement — one year on Replied, post #38 · Clinical › Comorbidities · 12 Jul 2026 · 0 likes Where a condition is well controlled and where it is not are different questions and the published data rarely distinguishes them. Happy to expand any of that if it is…
Common supplements people ask about, assessed one at a time Replied, post #34 · Practice › Interactions · 11 Jul 2026 · 1 like I think the common supplements question is answerable and has not been answered, which is a more optimistic position than most of this thread.
Journal club: indirect comparison between two programmes, defended and attacked Replied, post #110 · Evidence › Journal club · 7 Jul 2026 · 14 likes Helpful, and short, which on this subject is harder than long.
[2026 update] Antibiotics and a course of something with delayed emptying Replied, post #4 · Practice › Interactions · 1 Jul 2026 · 2 likes Good question, well framed, and I would like to see it answered properly.
A pooled estimate that changed when one trial was added Replied, post #16 · Evidence › Meta-analyses · 29 Jun 2026 · 0 likes Quietly grateful for the plain phrasing. Not every thread gets that.
What I would want from a home test that does not exist yet — what changed since Replied, post #65 · Analytics › Home & field testing · 23 Jun 2026 · 26 likes Ultraviolet absorbance at 280 nanometres estimates concentration for peptides containing aromatic residues and gives nothing for peptides that do not. Knowing which…
Why a glucagon receptor agonist in a weight-loss compound is not a contradiction Replied, post #11 · Compounds › Retatrutide · 22 Jun 2026 · 7 likes Confirming post #8 from a second method, which matters more than confirming it from a second person. Glucagon receptor agonist is a good example of a question where the…
The most useful thing you learned here that was not the answer you came for Replied, post #51 · Lounge › Off topic · 17 Jun 2026 · 0 likes That is true everywhere. The reference material that gets used is the material that answers a question you have at the moment you have it, and glamour has nothing to do…
I joined for one answer and stayed for a year — what changed my mind Replied, post #26 · Start Here › Welcome · 17 Jun 2026 · 0 likes Nothing here requires expertise. The experienced members here got that way by posting questions, not by knowing the answer before they showed up. If you know something…
Alcohol: what is documented and what is folklore Replied, post #60 · Practice › Interactions · 16 Jun 2026 · 7 likes Fair, and the limits you put on it are the part I will remember.
Racemisation and why it is invisible to a mass measurement Replied, post #105 · Analytics › Impurities & related substances · 14 Jun 2026 · 4 likes That is clearer than the version I had in my head. Thank you.
Oral versus injectable exposure: comparing apples to a different fruit — a second dataset Replied, post #24 · Compounds › Oral incretins · 8 Jun 2026 · 4 likes Tablet integrity matters more than people expect for a formulation that depends on an absorption enhancer released at a particular place. Splitting or crushing is not a…
A certificate whose chromatogram axes do not match its stated method — one year on Replied, post #105 · Sourcing › Red flags · 7 Jun 2026 · 2 likes That is the distinction I keep failing to hold on to. Written down now.
Submitting a sample: the process end to end Replied, post #4 · Sourcing › Independent verification · 6 Jun 2026 · 4 likes The opening post describes the usual case. This is about the unusual one. A record with four results over sixteen months is a thin record rather than a bad one, and the…
Revisiting: PCOS and metabolic overlap: what is and is not studied Replied, post #34 · Clinical › Comorbidities · 29 May 2026 · 0 likes Everything in post #32 holds. The case it does not cover is the one I have. Marking my uncertainty on PCOS and metabolic overlap explicitly. I am confident about the…
Dizziness on standing: the ordinary explanation first — one year on Replied, post #6 · Nutrition & Training › Hydration & electrolytes · 21 May 2026 · 0 likes Building on post #3 rather than restating it. The most useful posts here describe what was measured, what was changed, and what happened, in that order. Adding it in…
[2026 update] Regional warehouse stock versus direct despatch Replied, post #76 · Sourcing › Logistics · 21 May 2026 · 2 likes Appreciated. The plain phrasing does more work here than a longer post would.
Coming back to: When a red flag was a misunderstanding, and the retraction Replied, post #5 · Sourcing › Red flags · 18 May 2026 · 1 like The opening post put the caveat in the right place and I want to underline it. A note on scope: what I am saying about red flag applies to the case in the first post…
Run-in periods and the population they select Replied, post #117 · Evidence › Trials · 14 May 2026 · 2 likes Before the thread moves on from run-in periods — what is the sample size behind the claim? I am not being difficult; I have seen the same figure quoted from an n of…
Revisiting: Can a home kit substitute for a laboratory report? A careful no Replied, post #11 · Analytics › Home & field testing · 22 Apr 2026 · 0 likes Reading rather than answering, but this is the post I would point somebody at.
Is "synergy" the right word for the combination data? Replied, post #7 · Compounds › Cagrilintide & amylin analogues · 21 Apr 2026 · 4 likes Post #4 answers the question as asked. The question underneath it is different. Published human data on cagrilintide alone is thinner than on the combination, which is…
The best-written scientific paper you have read Replied, post #8 · Lounge › Off topic · 17 Apr 2026 · 12 likes Two claims get bundled together under best-written scientific paper and they need separating. The descriptive one — this is what was observed — is usually well…
Oral semaglutide bioavailability and its variability between people Replied, post #44 · Compounds › Oral incretins · 25 Mar 2026 · 2 likes Everything in post #43 holds. The case it does not cover is the one I have. Why administration conditions matter for oral semaglutide and not for injectables: the oral…
Pre-registering a personal experiment, seriously — a second dataset Replied, post #42 · Research Methods › N-of-1 designs · 12 Mar 2026 · 0 likes Answering the question post #38 raises rather than the one it answers. Pre-registering a personal experiment sits at the boundary between what this community can…
Grapefruit: why this class is not the class that cares Replied, post #12 · Practice › Interactions · 5 Mar 2026 · 19 likes One caution on grapefruit: everything above assumes the underlying documentation is what it claims to be. That assumption is doing real work and is rarely stated.
Second pass at: Where impurities in solid-phase peptide synthesis come from Replied, post #12 · Analytics › Impurities & related substances · 21 Feb 2026 · 12 likes My position on impurities in solid-phase peptide synthesis is current rather than settled. I have revised it once already and I expect to again, so treat it accordingly.
When your prescriber and the evidence disagree Replied, post #5 · Clinical › Prescriber conversations · 20 Feb 2026 · 19 likes Acknowledging rather than arguing. The reasoning holds as far as I can follow it.
Search filters: what is missing Replied, post #27 · Meta › Site feedback · 15 Feb 2026 · 23 likes Seconding that. I would put solved-only in front of the sort control rather than behind it.
Mass error in ppm: the arithmetic and the caveat Replied, post #39 · Analytics › Mass spectrometry · 13 Feb 2026 · 27 likes Sample preparation for mass spectrometry can itself introduce modifications, particularly oxidation. A finding at trace level may be telling you about the preparation…
Trifluoroacetate content and its consequences Replied, post #30 · Analytics › Impurities & related substances · 27 Jan 2026 · 14 likes I keep a log for trifluoroacetate content specifically because my memory of it turned out to be systematically wrong in one direction. Six weeks of notes cost nothing…
Second pass at: Metformin co-administration and additive GI effects Replied, post #35 · Practice › Interactions · 18 Jan 2026 · 0 likes Adding a small correction to the Metformin co-administration summary above rather than a disagreement with it. The substance holds; one of the figures is out by a…
What to include when your question involves a chromatogram Replied, post #50 · Start Here › How to Ask · 17 Jan 2026 · 0 likes Right, and stated more narrowly than I would have dared to state it.
Muscle cramps: the ordinary causes before the exotic ones Replied, post #21 · Practice › Side effects · 14 Jan 2026 · 31 likes Worth separating two things that post #17 runs together. Adding a reference point for muscle cramps. Mine is a single case, collected without controls, and I am posting…
A partial dose because the pen emptied mid-injection Replied, post #113 · Practice › Administration · 11 Jan 2026 · 0 likes Genuine question rather than a rhetorical one: has anyone here actually observed partial dose because the pen, as opposed to read about it? The thread is long and I…
Reading U-100 graduations, with a conversion table Replied, post #5 · Devices › Syringes & needles · 1 Jan 2026 · 0 likes Sharps containers are a legal requirement for disposal in several jurisdictions and a sensible precaution everywhere. A rigid sealed container is the minimum. Nothing…
How to read a forest plot, properly, from scratch Replied, post #77 · Evidence › Trials · 28 Dec 2025 · 25 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…
Interpreting a result that disagrees with the supplier's certificate Replied, post #25 · Sourcing › Independent verification · 27 Nov 2025 · 0 likes The bit of interpreting a result that nobody enjoys is that the answer changes depending on what you are trying to decide with it. Say what the decision is and the…
[2026 update] How much of the diluent volume the powder itself displaces Replied, post #16 · Practice › Reconstitution · 23 Nov 2025 · 15 likes A 0.3 mL barrel has more space between graduations than a 1 mL barrel for the same volume, which is the entire practical argument for the smaller syringe. Resolution,…
"Greater than or equal to 99%" as a specification rather than a result Replied, post #67 · Analytics › COA interpretation · 8 Nov 2025 · 27 likes Worth separating two things that post #65 runs together. A chromatogram supplied as a small image is legible for peak shape and not for baseline detail. That is enough…
Second pass at: Journal club: STEP 4 and what a withdrawal design can prove Replied, post #87 · Evidence › Journal club · 2 Nov 2025 · 0 likes Second this, and I would have said it less carefully.
Follow-up: What a seizure notice actually says Replied, post #30 · Sourcing › Logistics · 26 Oct 2025 · 9 likes Answering the question post #28 raises rather than the one it answers. Taking seizure notice seriously for a moment rather than deflecting: the honest position is that…
Titles that describe the question, not the situation Replied, post #129 · Start Here › How to Ask · 23 Oct 2025 · 0 likes Taking post #127 at face value and following it one step further. A definition problem is doing most of the work in this titles discussion. Once the term is pinned down…
"Should I double up?" — answered once, at length, calmly Replied, post #24 · Practice › Administration · 14 Oct 2025 · 13 likes Agreed on all of that, and I have nothing to add to it.
Refrigerated versus room temperature: the trade-off stated plainly — what changed since Replied, post #2 · Practice › Storage & stability · 5 Sep 2025 · 1 like The honest summary: keep it dry until you need it, keep it cold once it is not, keep it dark, do not cycle the temperature, and treat any period at room temperature as…
Asking about a compound your prescriber has not heard of Replied, post #146 · Clinical › Prescriber conversations · 2 Sep 2025 · 0 likes A second opinion is a normal part of medicine rather than an accusation, and asking how to obtain one is a legitimate question.
When a preprint is the best available evidence and we say so Replied, post #100 · Evidence › Preprints · 26 Aug 2025 · 1 like Retractions and corrections do not propagate well from preprint servers. A citation that was fine when made can quietly become wrong.
[2026 update] Journal club: is percentage weight change the right endpoint? Replied, post #97 · Evidence › Journal club · 23 Aug 2025 · 1 like Everything in post #93 holds. The case it does not cover is the one I have. Sessions on negative or null results are consistently the most instructive and the hardest…
Tirzepatide in type 2 diabetes: the SURPASS programme, summarised honestly Replied, post #144 · Compounds › Tirzepatide · 23 Jul 2025 · 1 like The GIP component: GIP receptor agonism is thought to amplify the GLP-1 effect on satiety and energy expenditure, but how much of tirzepatide's effect is that and how…
Journal club: the CagriSema phase 2 combination paper — a second dataset Replied, post #73 · Evidence › Journal club · 9 Jul 2025 · 0 likes TRIUMPH (ongoing): Retatrutide phase 3. No results yet. Nothing should be attributed to it because it has not finished. When it does, this discussion will return to it.
Follow-up: History of disordered eating and why it changes the conversation Replied, post #31 · Clinical › Special populations · 28 Jun 2025 · 2 likes Body weight at the extremes of the studied range affects exposure and the trials rarely reported enough to say by how much. A qualification I should have led with…
Journal club: STEP 4 and what a withdrawal design can prove Replied, post #64 · Evidence › Journal club · 26 Jun 2025 · 29 likes The confident answers on STEP 4 and the well-sourced answers are not the same answers, which is the most useful thing I have learned reading this category.
Ipamorelin selectivity claims and where they came from Replied, post #43 · Compounds › Secretagogues & GH axis · 2 Jun 2025 · 12 likes Worth separating two things that post #41 runs together. The question underneath ipamorelin selectivity claims is usually "how would I tell?" rather than "what is…
A well-designed study with a badly written abstract Replied, post #93 · Evidence › Study critique · 19 May 2025 · 5 likes Criticism is more useful when it is narrower. "The trial answers a different question from the one being asked" is actionable; "the trial is flawed" is not. That…
Trial registration and comparing the protocol with the paper Replied, post #7 · Evidence › Trials · 10 May 2025 · 9 likes The figure that circulates in coverage is almost always whichever estimand gives the larger effect. That is not fraud; it is selection, and it is why the paper matters…
Escalating every six weeks instead of four: what I observed over eight months — one year… Replied, post #25 · Practice › Dosing & titration · 6 May 2025 · 20 likes Concentration and dose get conflated constantly in this subcategory. Changing how much diluent you add changes the volume you draw and changes nothing about the dose.
Triple agonism: additive, synergistic, or neither? Replied, post #40 · Compounds › Retatrutide · 26 Apr 2025 · 0 likes A methods point on triple agonism rather than a substantive one: if the comparison is not like for like, the difference you are measuring is the difference in method.
Cost per milligram, computed honestly across formats — the long version Replied, post #75 · Access › Pricing · 23 Apr 2025 · 0 likes The most useful pricing posts here are the ones that show the arithmetic rather than the conclusion.
Which panel is worth repeating and which is worth ignoring Replied, post #6 · marked as the solution · Clinical › Bloodwork · 20 Apr 2025 · 15 likes Where I would push back on the panel consensus is the confidence, not the direction. The direction looks right. The confidence is borrowed.
Hepatic steatosis: what the MASH trial evidence supports Replied, post #20 · Clinical › Comorbidities · 16 Apr 2025 · 0 likes The honest answer to most questions here is that the trial population did not include the case being asked about, and that saying so is more useful than filling the gap…
Second pass at: Pen dose counters: what a click does and does not guarantee Replied, post #5 · Devices › Pens & autoinjectors · 22 Mar 2025 · 12 likes Post #3 describes the usual case. This is about the unusual one. Off-label dosing with a pen: if you want to deliver a dose different from the pen's pre-set steps…
Residual solvents and scavengers: what is looked for Replied, post #4 · Analytics › Impurities & related substances · 15 Mar 2025 · 21 likes Off-target structures: if the sequence synthesis goes wrong, a completely different amino acid can be incorporated. The resulting off-target peptide is a structural…
Review: a draft on reconstitution arithmetic, with objections Replied, post #59 · Documentation › Doc review · 15 Mar 2025 · 0 likes Nothing in a maintained document is medical advice and the review should confirm the page says so where it matters rather than only in a footer. This has been discussed…
Coming back to: Official shortage notices and what they authorise Replied, post #10 · Access › Shortages · 10 Feb 2025 · 0 likes Narrowing post #7, because the general version has more than one answer. Where a shortage forces a gap, the pharmacokinetics mean a missed week is a perturbation rather…
Washout: how long is long enough, and for what purpose Replied, post #3 · Pharmacology › Pharmacokinetics · 8 Feb 2025 · 10 likes I had written a reply contradicting the opening post and deleted it. Here is what survived. Adding a null result on washout. I looked, carefully, and found nothing, and…
Why mass spectrometry cannot tell you about an epimer Replied, post #31 · Analytics › Mass spectrometry · 18 Jan 2025 · 0 likes Calibration matters: a high-resolution instrument out of calibration can report mass with ppm error large enough to be uninformative. Check when the instrument was last…
Follow-up: Individual participant data versus aggregate data Replied, post #34 · Evidence › Meta-analyses · 9 Jan 2025 · 0 likes This is the answer, and the reason it is the answer is the more useful part.
Oral semaglutide bioavailability and its variability between people — a second dataset Replied, post #132 · Compounds › Oral incretins · 29 Dec 2024 · 0 likes Oral bioavailability is variable between people. Some people absorb well; others absorb poorly. That inter-individual variation is larger than with injectables and is…
A 5 mg vial and a 0.25 mg dose: the arithmetic in full — the long version Started this topic · Practice › Reconstitution · 18 Dec 2024 · 5 likes On the subject in the title: A 5 mg vial and a 0.25 mg dose: the arithmetic in full — the long version Working notes rather than a conclusion. A narrow question about 5…
Coming back to: Grapefruit: why this class is not the class that cares Replied, post #34 · Practice › Interactions · 6 Dec 2024 · 0 likes Post #31 is the version of this I will quote in future. One addition. Alcohol: no absolute contraindication but it raises gastrointestinal irritation risk and this drug…
[2026 update] New subcategory: rationale and scope Replied, post #5 · Meta › Announcements · 14 Nov 2024 · 6 likes Post #4 and I disagree about the size of the effect, not about the direction. The most useful thing anyone has posted about New subcategory in this category was a table…
Second pass at: Reimbursement variation across member states Replied, post #27 · Regional › European Union · 2 Nov 2024 · 0 likes Where a member reports an access decision, the stated criterion is the generalisable part and the outcome is not.
Amylin analogue mechanism: satiety signalling separate from GLP-1 Replied, post #17 · Compounds › Cagrilintide & amylin analogues · 1 Nov 2024 · 2 likes Research-use-only cagrilintide is not approved for human use and the published evidence base is a clinical-trial evidence base. Those two facts sit uncomfortably…
[2026 update] Journal club: SURPASS-2 and the semaglutide 1 mg comparator Replied, post #20 · Evidence › Journal club · 30 Oct 2024 · 6 likes Everything in post #16 holds. The case it does not cover is the one I have. Something worth flagging about SURPASS-2: the strongest-sounding claims in this thread are…
Follow-up: Dead volume across syringe and needle combinations Replied, post #48 · Devices › Syringes & needles · 12 Oct 2024 · 0 likes Adding the measurement that post #45 says would settle it. Dead volume across syringe came up in a thread eighteen months ago and was answered well. I cannot find it,…
What a stability-indicating method is and how you demonstrate one — one year on Replied, post #47 · Analytics › Method validation · 7 Oct 2024 · 24 likes Post #43 put the caveat in the right place and I want to underline it. Forced degradation studies: deliberately stress the material with acid, base, oxidant, heat,…
Hepatic effects of glucagon receptor agonism: the mechanistic worry Replied, post #54 · Compounds › Retatrutide · 23 Sep 2024 · 20 likes Post #53 is the version of this I will quote in future. One addition. Nausea and vomiting were dose-related in the phase 2 work, as they are throughout this class. What…
Second pass at: Sodium, potassium and magnesium when intake drops Replied, post #110 · Nutrition & Training › Hydration & electrolytes · 23 Sep 2024 · 0 likes Rapid correction of a genuine abnormality can be more dangerous than the abnormality, which is another reason this belongs in clinical hands. The variance between…
Blind submission and why it changes minds Replied, post #42 · Sourcing › Independent verification · 22 Aug 2024 · 8 likes Reframing blind submission 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…
Coming back to: Purity assay versus content assay: two different numbers Replied, post #7 · Analytics › COA interpretation · 7 Aug 2024 · 23 likes The most useful reply I ever got about Purity assay versus content assay was a request to state my units. It sounds like pedantry and it has saved me twice.
Two sessions a week versus four: what the evidence supports — a second dataset Replied, post #32 · Nutrition & Training › Resistance training · 14 Jul 2024 · 14 likes Reduced appetite makes fuelling a session harder, and that is a practical problem with practical solutions rather than a reason to stop.
Assessing a warm arrival: the decision process — one year on Replied, post #28 · Sourcing › Logistics · 29 May 2024 · 7 likes Narrowing post #26, because the general version has more than one answer. Before the thread moves on from Assessing a warm arrival — what is the sample size behind the…