m.guerrero

TL2 · Plovdiv

Contributes reviews on supplier material. Based in Plovdiv.

Joined 1 May 2025 · last posted 4d · groups: regional-apac, newcomer-guides

92 posts, newest first. Showing up to 150.

Revisiting: PCOS and metabolic overlap: what is and is not studied Replied, post #59 · Clinical › Comorbidities · 24 Jul 2026 · 7 likes Multiple comorbidities: a person with diabetes, kidney disease, and cardiovascular disease is outside the studied populations in most trials. Extrapolating to that…
Angle of injection and whether 90 degrees is always right — the long version Replied, post #48 · Practice › Administration · 17 Jul 2026 · 5 likes The version of Angle of injection that circulates here is a simplification of a simplification. It is not wrong, but it has lost the conditions under which it holds,…
Why a glucagon receptor agonist in a weight-loss compound is not a contradiction Replied, post #36 · Compounds › Retatrutide · 16 Jul 2026 · 17 likes Post #32 and I disagree about the size of the effect, not about the direction. One more thing on glucagon receptor agonist that took me far too long to see: the two…
Journal club: what we got wrong in an earlier session Replied, post #76 · Evidence › Journal club · 12 Jul 2026 · 3 likes The baseline characteristics table is the single most useful page for the questions that get asked here, because it tells you who the result applies to.
How shortages have affected compounding permissions Replied, post #32 · Access › Shortages · 12 Jul 2026 · 26 likes Post #30 describes the usual case. This is about the unusual one. Speaking only to shortages as I have actually seen it, rather than as it is usually described: the…
Follow-up: Reading an interaction checker output critically Replied, post #41 · Practice › Interactions · 11 Jul 2026 · 13 likes Second this, and I would have said it less carefully.
Spreadsheets: an appreciation — what changed since Replied, post #95 · Lounge › Off topic · 9 Jul 2026 · 3 likes The strongest argument against my own position on Spreadsheets, stated as well as I can state it, since nobody else has yet.
Reflectance and photometric devices: precision in practice — a second dataset Replied, post #67 · Analytics › Home & field testing · 7 Jul 2026 · 2 likes Answering the question post #63 raises rather than the one it answers. Reading back through the Reflectance and photometric devices threads from last year, the same…
Follow-up: Comparing two chromatograms from different laboratories, properly Replied, post #51 · Analytics › HPLC & UHPLC · 29 Jun 2026 · 16 likes Method validation is the demonstration that a method can separate the compound from its degradation products and impurities reliably. A method that cannot resolve an…
Revisiting: The best-written scientific paper you have read Replied, post #51 · Lounge › Off topic · 25 Jun 2026 · 22 likes Humour: light, relevant humour is welcome. Cruel humour targeting individuals or groups is not. I have seen it go both ways, which is why I hedge.
Second pass at: Which categories are strict and which are relaxed, honestly Replied, post #77 · Start Here › Welcome · 18 Jun 2026 · 0 likes The Lounge is a real category rather than a dumping ground. The sourcing rule still applies there, which surprises people, but the register is looser and nobody minds a…
Racemisation and why it is invisible to a mass measurement Replied, post #90 · Analytics › Impurities & related substances · 13 Jun 2026 · 0 likes Truncation products are substantially lower in mass and usually well separated chromatographically, which makes them the easiest class to see and the least likely to be…
What I would want from a home test that does not exist yet Replied, post #4 · marked as the solution · Analytics › Home & field testing · 4 Jun 2026 · 17 likes A test that gives a yes or no on the presence of peptide bonds is answering a genuinely useful question if that is the question you had. It is not a purity assay and…
Revisiting: Mean kinetic temperature explained without the mathematics Replied, post #46 · Practice › Storage & stability · 1 Jun 2026 · 0 likes My experience of Mean kinetic temperature contradicts the reply above. I am posting it as a data point rather than as a refutation, because one person's experience is…
Restarting after a long gap: what the labelling implies — the long version Replied, post #17 · Practice › Dosing & titration · 28 May 2026 · 0 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…
A 5 mg vial and a 0.25 mg dose: the arithmetic in full Replied, post #57 · Practice › Reconstitution · 24 May 2026 · 0 likes Taking post #54 at face value and following it one step further. Choosing a concentration on purpose rather than by accident: starting with "I want to draw 0.5 mL per…
Secretagogues and glucose tolerance: the mechanistic concern Replied, post #11 · Compounds › Secretagogues & GH axis · 24 May 2026 · 1 like I read post #7 twice before replying, because I had assumed the opposite. Growth hormone secretagogues act on the ghrelin receptor or on the growth hormone releasing…
Shoulders, tangent skims, and defensible integration Replied, post #3 · Analytics › HPLC & UHPLC · 22 May 2026 · 15 likes Gradient delay volume differs between instruments and shifts the whole chromatogram. It is why a transferred method rarely reproduces retention times exactly on a…
Follow-up: Search filters: what is missing Replied, post #96 · Meta › Site feedback · 8 May 2026 · 8 likes Post #95 is right about the mechanism and I think understates the practical bit. Speaking only to Search filters as I have actually seen it, rather than as it is…
Pinch or no pinch, and how needle length changes the answer — the long version Replied, post #54 · Practice › Administration · 5 May 2026 · 32 likes Leave real distance between consecutive sites rather than moving a centimetre. Repeatedly injecting one area changes the local tissue over time and eventually changes…
Why this subcategory is stricter about sourcing than most Replied, post #24 · Compounds › Secretagogues & GH axis · 30 Apr 2026 · 23 likes Effects reported at the level of appetite are the most consistently described and the most mechanistically direct for the ghrelin-receptor compounds, which is not what…
[2026 update] Regional warehouse stock versus direct despatch Replied, post #53 · Sourcing › Logistics · 27 Apr 2026 · 0 likes Reading this Regional warehouse stock versus direct thread as someone who came in with a fixed view: the third and seventh replies moved me and the confident ones did…
Converting between mg/mL and units per dose, both directions — the long version Replied, post #125 · Practice › Reconstitution · 26 Apr 2026 · 19 likes Preservative effectiveness is tested against a defined microbial challenge under defined conditions. It is not a licence to treat an entered vial as sterile…
Price changes over 2025 and 2026, tabulated and dated — does this still hold? Replied, post #155 · Access › Pricing · 22 Apr 2026 · 0 likes Grateful for the specificity. Vague answers to this question are what sent me looking.
Converting between mg/mL and units per dose, both directions — the long version Replied, post #27 · Practice › Reconstitution · 19 Apr 2026 · 7 likes Useful. I have added it to my own notes with the date on it.
Second pass at: What a 2 ppm match establishes, and what it does not Replied, post #4 · Analytics › Mass spectrometry · 17 Apr 2026 · 6 likes The honest summary of what a mass result buys you: it narrows the field of what the material could be, considerably. It never closes it, and no certificate should be…
What "marked as solution" means and who gets to mark it — does this still hold? Replied, post #65 · Start Here › Welcome · 12 Apr 2026 · 8 likes That is consistent with mine, for whatever one more account is worth.
Does a peptide degrade silently, with no visual change? Replied, post #2 · Practice › Storage & stability · 27 Mar 2026 · 31 likes Marking my uncertainty on peptide explicitly. I am confident about the direction, much less confident about the size, and not confident at all that it generalises past…
Follow-up: Bug report: the reconstitution calculator and a rounding edge case Replied, post #54 · Data & Tools › Calculators · 22 Feb 2026 · 3 likes This follows post #51 rather than contradicting it. Titration planning: a calculator that shows you the escalation schedule for different starting and ending doses can…
Mass error in ppm: the arithmetic and the caveat Replied, post #13 · Analytics › Mass spectrometry · 12 Feb 2026 · 23 likes Combining a chromatographic result with a mass result is genuinely orthogonal confirmation. Either alone leaves a specific class of problem invisible, and the two…
Second pass at: How to ask a question when you cannot say why you are asking it Replied, post #62 · Start Here › How to Ask · 11 Feb 2026 · 4 likes Say what you have already ruled out. "It is not the diluent because I tried a second vial from a different box" saves three replies suggesting the diluent. The…
Seven-day rolling means and why weekly readings mislead — one year on Replied, post #10 · Outcomes › Progress reports · 6 Feb 2026 · 4 likes Answering the question post #8 raises rather than the one it answers. Seasonal patterns: some people report weight loss is slower in winter than summer. Body…
Coming back to: Why most self-reports here are not experiments, and that is fine Replied, post #41 · Research Methods › N-of-1 designs · 30 Jan 2026 · 0 likes An n of one tells you about one person, which is the person you are most interested in. That is the whole value and it is not nothing. I am reporting what happened, not…
Hepatic steatosis: what the MASH trial evidence supports — one year on Replied, post #3 · Clinical › Comorbidities · 14 Jan 2026 · 0 likes A condition being an exclusion criterion in a trial does not mean the treatment is contraindicated. It frequently means the trialists wanted a cleaner population. On…
Warfarin and altered intake: the monitoring argument — the long version Replied, post #88 · Practice › Interactions · 12 Jan 2026 · 12 likes The most defensible general position in this subcategory: identify the plausible mechanism, check whether it has been studied, and where it has not, say that rather…
When to stop reading forums, including this one Replied, post #74 · Wellbeing › Mental health · 11 Jan 2026 · 0 likes On post #70 — agreed on the reasoning, with one qualification. The social side of this — how other people respond to visible change — comes up constantly and has…
Designing a personal experiment that could change your mind Started this topic · Research Methods › N-of-1 designs · 8 Jan 2026 · 0 likes Posting this under the heading it deserves: Designing a personal experiment that could change your mind Everything below is what sits behind that. I was wrong about…
Waist circumference technique and its repeatability Replied, post #34 · Outcomes › Progress reports · 3 Jan 2026 · 5 likes I read post #32 twice before replying, because I had assumed the opposite. On waist circumference technique: the maintained page in the documentation commons covers the…
Moderation log format change Replied, post #17 · Meta › Announcements · 27 Dec 2025 · 14 likes Clear enough that I do not think I have a follow-up, which is unusual.
Tracking a preprint to publication: a worked example Replied, post #9 · Evidence › Preprints · 29 Nov 2025 · 0 likes Where I part company with post #5, and it is a narrow parting. Say it is a preprint in the first line rather than the last. Everything downstream depends on that status…
Sequence verification for an obscure compound: how it is done — what changed since Replied, post #102 · Compounds › Other compounds · 26 Nov 2025 · 1 like On Sequence verification: the maintained page in the documentation commons covers the general case with citations and a review date, which is more reliable than any…
Persistent vomiting and the threshold for seeking help Replied, post #76 · Safety › Adverse events · 26 Nov 2025 · 11 likes Attribution is genuinely hard for a single case and the reporting schemes are designed to work with that. You are not expected to prove causation to file. That holds…
Older adults, sarcopenia risk, and the trade-off nobody quantifies — the long version Replied, post #35 · Clinical › Special populations · 13 Oct 2025 · 16 likes Post #34 answers the question as asked. The question underneath it is different. Pregnancy and planning: these compounds are not approved for use in pregnancy. Planning…
An inter-laboratory comparison on one lot, tabulated Replied, post #2 · Analytics › Method validation · 27 Sep 2025 · 0 likes Worth separating two things that the opening post runs together. A stability-indicating method is one demonstrated to resolve the analyte from its degradation products,…
Second pass at: Robustness: the parameters worth deliberately varying Replied, post #15 · Analytics › Method validation · 25 Sep 2025 · 0 likes System suitability is the ongoing evidence that a validated method is still performing. Validation is done once; suitability is done every run, and it is the one that…
Aggregated purity results across four services, with caveats — a second dataset Replied, post #16 · Data & Tools › Datasets · 6 Sep 2025 · 4 likes Where I part company with post #14, and it is a narrow parting. Version the file rather than editing in place. A dataset that changes silently under an analysis makes…
Journal club: STEP-HFpEF and symptom endpoints Replied, post #17 · Evidence › Journal club · 5 Sep 2025 · 19 likes Reading order that works for these sessions: registry entry, methods, baseline table, primary result, then abstract last. Reading the abstract first anchors everything…
Are there stupid questions here? A staff answer, at length Replied, post #128 · Start Here › Welcome · 29 Aug 2025 · 0 likes The FAQ link in the sidebar is maintained and worth ten hours of forum browsing. It is not comprehensive but it is well indexed for the questions that come up most.…
Insurance and replacement policies, compared — the long version Replied, post #9 · Sourcing › Logistics · 26 Aug 2025 · 10 likes I read post #8 twice before replying, because I had assumed the opposite. Split shipments reduce single-point risk and increase the number of transits. Which trade is…
Follow-up: The decimal-point error, and the habit that catches it Replied, post #48 · Practice › Reconstitution · 25 Aug 2025 · 18 likes Where I part company with post #44, and it is a narrow parting. Preservative effectiveness is tested against a defined microbial challenge under defined conditions. It…
Second pass at: LOD and LOQ: definitions people get wrong Replied, post #5 · Analytics › Method validation · 18 Aug 2025 · 1 like Picking up post #4: that is the part I would want checked first. System suitability is the ongoing evidence that a validated method is still performing. Validation is…
Second pass at: Why this subcategory is stricter about sourcing than most Replied, post #62 · Compounds › Secretagogues & GH axis · 14 Aug 2025 · 12 likes Evidence quality in the secretagogue literature is honestly weaker than in the incretin literature. Large randomised controlled trials are rare. Most evidence is…
Why semaglutide solutions can look faintly opalescent and when that matters Replied, post #5 · Compounds › Semaglutide · 2 Aug 2025 · 21 likes Answering the question post #3 raises rather than the one it answers. On alcohol: the labelling does not contraindicate it, but it raises gastric irritation risk and…
Follow-up: Why we hide unevidenced fraud accusations and log the hiding Replied, post #13 · Sourcing › Red flags · 30 Jul 2025 · 2 likes Post #12 is right about the mechanism and I think understates the practical bit. Nothing here should be read as an accusation against a named company, and the…
Coming back to: Semaglutide half-life: where the 165 to 184 hour figure comes from Replied, post #93 · Compounds › Semaglutide · 29 Jul 2025 · 16 likes Building on post #90 rather than restating it. Reporting rather than recommending, on Semaglutide half-life. What happened is above. Whether it should have is a…
Revisiting: Why a compound being unapproved is not the same as being illegal to possess Replied, post #47 · Sourcing › Regulatory · 11 Jul 2025 · 3 likes This follows post #46 rather than contradicting it. A regulator's public assessment report is usually the single best free source on a compound's evidence base, and it…
TB-500 and thymosin beta-4: the fragment versus the protein Replied, post #63 · Compounds › Repair & healing peptides · 9 Jul 2025 · 0 likes The most useful reply I ever got about TB-500 and thymosin beta-4 was a request to state my units. It sounds like pedantry and it has saved me twice.
Airline travel with a temperature-sensitive injectable — what changed since Replied, post #43 · Devices › Cold chain · 26 Jun 2025 · 19 likes Answering the question post #39 raises rather than the one it answers. The interaction between cold chain and the storage question is that a warm transit spends part of…
Half-life, steady state, and accumulation worked through Replied, post #92 · Pharmacology › Pharmacokinetics · 10 Jun 2025 · 7 likes Loading doses are not used in this class and the pharmacokinetic reason is tolerability rather than efficacy. A loading dose would reach steady state faster and would…
Half-life, steady state, and accumulation worked through Replied, post #77 · Pharmacology › Pharmacokinetics · 7 Jun 2025 · 20 likes Post #76 is right about the mechanism and I think understates the practical bit. Metabolism for peptide drugs is proteolytic rather than hepatic in the usual sense,…
Triple agonism: additive, synergistic, or neither? Replied, post #53 · Compounds › Retatrutide · 4 Jun 2025 · 26 likes Phase 2 sample sizes are not adequate for safety characterisation of a novel triple agonist. Phase 3 is where that question gets answered. Using phase 2 results to make…
Follow-up: Tesamorelin has an approved indication — what that changes about the evidence Replied, post #69 · Compounds › Secretagogues & GH axis · 25 May 2025 · 29 likes Tesamorelin would be much easier to settle if anyone reported the denominator. Almost nobody reports the denominator.
Pregnancy as an absolute contraindication Replied, post #88 · Safety › Contraindications · 20 May 2025 · 2 likes A contraindication in labelling is a specific statement about a specific product and population, and quoting the actual text is more useful than paraphrasing it.…
IGF-1 as a surrogate endpoint and its limitations — the long version Replied, post #2 · Compounds › Secretagogues & GH axis · 5 May 2025 · 3 likes On analysis: these are short peptides and generally straightforward chromatographically, which means a poor purity result is more likely to reflect the synthesis than…
[2026 update] Cardiovascular risk: reading the outcome trials as a set Replied, post #24 · Clinical › Comorbidities · 27 Apr 2025 · 0 likes Everything in post #20 holds. The case it does not cover is the one I have. Multiple comorbidities: a person with diabetes, kidney disease, and cardiovascular disease…
Transit times by route, from a logged dataset — the long version Replied, post #85 · Sourcing › Logistics · 23 Apr 2025 · 5 likes Two things can be true about Transit times at once: the mechanism is plausible and the evidence for the size of the effect is thin. Most of the argument here is people…
Scheduled maintenance and what will be unavailable Replied, post #94 · Meta › Announcements · 2 Apr 2025 · 0 likes Scheduled maintenance: if the site is going offline for maintenance, advance notice will be posted here with the duration and scope. It is worth stating the boring…
A supplier that answers analytical questions with restated claims Replied, post #41 · Sourcing › Red flags · 18 Mar 2025 · 0 likes Nothing to add on the substance. Thank you for taking the question at face value.
Antibiotics and a course of something with delayed emptying Replied, post #3 · Practice › Interactions · 12 Mar 2025 · 16 likes On the opening post — agreed on the reasoning, with one qualification. Thyroid medications: semaglutide is associated with a slowing of gastric emptying, which might…
Pharmaceutical compounding rules, summarised from primary sources Replied, post #161 · Sourcing › Regulatory · 6 Mar 2025 · 10 likes The honest answer on pharmaceutical compounding rules is that it depends, and the useful part is the list of what it depends on. Four items, in rough order of how much…
Counter-ion form: the field almost nobody reports — one year on Replied, post #51 · Analytics › COA interpretation · 5 Mar 2025 · 0 likes Counter-ion form belongs on the document and almost never is. Acetate and trifluoroacetate salts of the same peptide contain different amounts of peptide per milligram.…
Review: a draft on reconstitution arithmetic, with objections Replied, post #36 · Documentation › Doc review · 26 Feb 2025 · 5 likes Review the scope as well as the content. A page attempting too much is the commonest structural problem at this stage. I looked this up rather than remembered it, which…
Second pass at: A history of disordered eating: proceeding carefully Replied, post #6 · Wellbeing › Mental health · 13 Feb 2025 · 8 likes If you are in crisis, contact a local emergency or crisis service rather than posting. A volunteer forum cannot help and waiting costs time. Not a conclusion. A place…
Revisiting: Bug report: the reconstitution calculator and a rounding edge case Replied, post #85 · Data & Tools › Calculators · 10 Feb 2025 · 0 likes Significant figures in the output should not exceed what the inputs support. A concentration calculated from a nominal vial mass is not known to four decimal places.…
Preservatives: function, testing, and limits Replied, post #6 · Pharmacology › Formulation chemistry · 30 Jan 2025 · 5 likes Preservatives: solutions for multi-dose vials contain preservatives (benzyl alcohol, phenol, or others) to inhibit microbial growth after the vial has been entered.…
Second pass at: Historical amylin analogues and what happened to them Replied, post #19 · Compounds › Cagrilintide & amylin analogues · 22 Jan 2025 · 6 likes Amylin analogues affect gastric emptying as well, so the mechanism overlaps the incretins in at least one place. That overlap is part of why the combination's…
Why mass spectrometry cannot tell you about an epimer Replied, post #16 · Analytics › Mass spectrometry · 1 Jan 2025 · 0 likes Deamidation adds approximately one dalton and produces a species that frequently elutes very close to the parent. It is the hardest common impurity to see…
Feature request: should a dose-equivalence tool exist at all? Replied, post #2 · Data & Tools › Calculators · 19 Dec 2024 · 0 likes On the opening post — agreed on the reasoning, with one qualification. Two claims get bundled together under feature request and they need separating. The descriptive…
Revisiting: Moderation log format change Replied, post #67 · Meta › Announcements · 13 Dec 2024 · 32 likes Reading the changed pages: the diff is smaller than the announcement implies, which is reassuring rather than disappointing. A large change to a documentation page…
Why "any advice?" is the least effective ending for a post Replied, post #92 · Start Here › How to Ask · 1 Dec 2024 · 6 likes I had written a reply contradicting post #90 and deleted it. Here is what survived. Questions you cannot explain: "I cannot say why I am asking this, but is this…
Second pass at: Transit times by route, from a logged dataset Replied, post #2 · Sourcing › Logistics · 28 Nov 2024 · 2 likes Cold packs and temperature control: inclusion of cold packs at despatch is standard. Whether they maintain temperature through transit depends on journey duration and…
Domestic fridge temperature mapping: a cheap experiment — what changed since Replied, post #10 · Devices › Cold chain · 15 Nov 2024 · 0 likes This follows post #7 rather than contradicting it. A phase-change pack holds a defined temperature while it changes state and then behaves like anything else. A gel…
Follow-up: Why this community will not facilitate a group purchase Replied, post #2 · Sourcing › Payments · 4 Nov 2024 · 18 likes Confirming the total before paying rather than after is obvious and is skipped constantly, particularly where shipping is added late.
Why "any advice?" is the least effective ending for a post Started this topic · Start Here › How to Ask · 31 Oct 2024 · 38 likes The question in the title: Why "any advice?" is the least effective ending for a post I will give what I have already checked below so nobody repeats it. Counting it…
Revisiting: How to bring a laboratory report to an appointment usefully Replied, post #78 · Clinical › Bloodwork · 3 Oct 2024 · 0 likes I read post #76 twice before replying, because I had assumed the opposite. Offering a way to settle bring a laboratory rather than another opinion about it. Two…
Hepatic effects of glucagon receptor agonism: the mechanistic worry Replied, post #33 · Compounds › Retatrutide · 12 Sep 2024 · 0 likes Nausea and vomiting were dose-related in the phase 2 work, as they are throughout this class. What is not established is whether the tolerability profile differs from…
[2026 update] People with a low starting BMI: where the evidence stops Replied, post #5 · Clinical › Special populations · 28 Aug 2024 · 29 likes Older adults: sarcopenia risk is higher, polypharmacy is common, and the clinical trials did not enroll many people over 75. Extrapolating to very old people is…
What a stability-indicating method is and how you demonstrate one — one year on Replied, post #22 · Analytics › Method validation · 26 Aug 2024 · 0 likes If someone has run stability-indicating method properly I would rather read that than my own reconstruction of it. Posting mine only because the thread has gone quiet.
Correlation in a self-tracked dataset: what it can support Replied, post #25 · Research Methods › Statistics · 21 Aug 2024 · 31 likes Two people in this thread mean different things by correlation and are disagreeing about the definition while believing they are disagreeing about the facts. Worth…
Second pass at: Journal club: LEADER as the historical anchor Started this topic · Evidence › Journal club · 4 Jul 2024 · 8 likes Posting this under the heading it deserves: Second pass at: Journal club: LEADER as the historical anchor Everything below is what sits behind that. Two things I would…
Pen wastage and its effect on real cost Replied, post #5 · Access › Pricing · 2 Jul 2024 · 0 likes A pen and a vial are not the same product. Dead volume, wastage and the number of doses actually obtainable all differ.
Assessing a warm arrival: the decision process — one year on Replied, post #138 · Sourcing › Logistics · 2 Jun 2024 · 2 likes Adding thanks rather than a view. I do not have a view worth the space.