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1.4k questions · page 57 of 60

27 votes0 answers12k views
Does racemisation dominate for orforglipron held at minus 20 °C?

Numbers first: racemisation · orforglipron · minus 20 °C. I suspect the usual explanation for this is wrong, or at least incomplete. I am aware this may have a boring…

peptide-stability
peptide-stability

The chemistry of peptide degradation: deamidation, oxidation, hydrolysis, aggregation and fibrillation, and how temperature, pH, ionic strength,…

832 questions
storage
storage

Storage conditions and their evidence base: minus twenty degrees for powder, refrigerated for solution, protection from light, and what the…

646 questions
hplc
hplc

Reverse-phase high-performance liquid chromatography, the workhorse purity method. Column chemistry, mobile-phase choice, gradient slope,…

466 questions
asked by meniscus_film 34k · 13 months ago
27 votes0 answers11k views
What does Medutest verification of Nantong Guangyuan Chemical actually cover?

Setup, so nobody has to ask: Medutest · Nantong Guangyuan Chemical. I would like help reading this properly rather than being told what conclusion to reach. I have…

vendor-investigate
vendor-investigate

VendorInvestigate, an independent vendor review and verification service. Use this tag for questions about its verification criteria, what a…

41 questions
vendor-vetting
vendor-vetting

Evaluating a supplier on evidence rather than reputation: testing history across batches, whether certificates are batch-specific, how failures…

436 questions
coa
coa

Certificates of analysis: what fields a useful one carries, how to tell a real analytical report from a marketing document, batch and lot…

749 questions
asked by tobias_reint 19k · 14 months ago
27 votes 5 answers11k views
Does racemisation of orforglipron at minus 80 °C show up as a loss of content or of purity?

Numbers first: racemisation · orforglipron · minus 80 °C. I can predict the outcome but I cannot explain it, which means I will get the next case wrong. I would like…

peptide-stability
peptide-stability

The chemistry of peptide degradation: deamidation, oxidation, hydrolysis, aggregation and fibrillation, and how temperature, pH, ionic strength,…

832 questions
content-assay
content-assay

Quantified content: how many milligrams of peptide are actually in the vial, measured against a calibrated reference standard. A separate test…

438 questions
purity
purity

Purity as chromatographic area per cent - the fraction of detected material that is your target peak. It says nothing about how much material is…

788 questions
asked by lukas_sedlacek 17k · 15 months ago
27 votes 3 answers11k views
Why is oral semaglutide only about 1% bioavailable, and what is SNAC actually doing?

I understand in general terms that peptides do not survive oral administration - stomach acid, proteases, and a wall of epithelium that evolved specifically to keep…

oral-glp1
oral-glp1

Oral routes for GLP-1 receptor agonism: peptide formulations rescued by absorption enhancers such as SNAC, and true small molecules that need no…

14 questions
semaglutide
semaglutide

A GLP-1 receptor agonist with a fatty-acid-acylated backbone and a roughly one-week half-life, marketed for type 2 diabetes and for weight…

360 questions
glp1-mechanism
glp1-mechanism

Receptor-level pharmacology: GLP-1R as a class B GPCR, cAMP and PKA signalling, biased agonism, internalisation and resensitisation, and the…

175 questions
dulaglutide
dulaglutide

A once-weekly GLP-1 receptor agonist built on an Fc fusion rather than fatty-acid acylation. Use this tag for questions about the fusion-protein…

14 questions
asked by sample_id 17k · 22 months ago
27 votes 5 answers11k views
How do I compare ERP and SGN on lead time to New Zealand?

What I am working with: ERP · SGN · New Zealand. I suspect the honest answer is that it depends, in which case I would like to know on what. Assume I can obtain…

vendor-comparison
vendor-comparison

Side-by-side comparison of suppliers on measurable axes - independently confirmed purity and content, lead time, cold-chain handling,…

351 questions
international-shipping
international-shipping

Cross-border movement of research material: transit lanes and their thermal profiles, tracked versus untracked, declaration accuracy, and what…

427 questions
cold-chain
cold-chain

Keeping material within a temperature window from manufacture to use: phase-change packs versus dry ice, thermal mass, transit-lane temperature…

524 questions
asked by fibre_or_fragment 12k · 7 months ago
27 votes 3 answers11k views
Why did my LDL-C rise 22% during the fastest phase of weight loss?

Twelve weeks in, losing roughly 1.1 kg a week, and my fasting LDL-C has gone from 2.7 to 3.3 mmol/L. Total cholesterol up from 4.6 to 5.2. Triglycerides down from 1.9…

lipids
lipids

Lipid response on treatment: triglycerides, LDL-C, non-HDL-C, ApoB and Lp(a), which of them move with weight loss, and why a fasting panel drawn…

112 questions
bloodwork
bloodwork

Laboratory monitoring: which panels are worth ordering, sensible intervals, reference-range versus optimal-range arguments, and how to read a…

284 questions
gallbladder
gallbladder

Cholelithiasis and cholecystitis risk during rapid weight loss and on treatment: how much is attributable to the rate of loss versus to the drug,…

14 questions
hydration
hydration

Fluid intake when thirst and intake cues are both blunted: how much of the early scale drop is fluid, how dehydration confounds a renal panel, and…

14 questions
asked by elke_brunner 14k · 14 months ago
27 votes 3 answers10k views
Is survodutide at 5 mg/mL stable enough for three weeks of multi-withdrawal use?

Concretely: survodutide · 5 mg/mL · three weeks. I want to know whether there is evidence behind this or only repetition. I have checked the obvious registries and…

peptide-stability
peptide-stability

The chemistry of peptide degradation: deamidation, oxidation, hydrolysis, aggregation and fibrillation, and how temperature, pH, ionic strength,…

832 questions
bacteriostatic-water
bacteriostatic-water

Water for injection containing roughly 0.9 per cent benzyl alcohol as a bacteriostatic agent. It suppresses growth in a multiple-withdrawal vial;…

112 questions
shelf-life
shelf-life

How long a preparation remains within specification: labelled expiry for a sealed lyophilised vial, beyond-use dating after reconstitution, and…

301 questions
asked by juan_esquivel 14k · 17 months ago
27 votes 5 answers10k views
Is a GLP-1 receptor agonist at 4 mg/mL stable enough for two weeks of multi-withdrawal use?

What I have: a GLP-1 receptor agonist · 4 mg/mL · two weeks. I am asking for verification rather than opinion, ideally with something I can read myself. It is…

peptide-stability
peptide-stability

The chemistry of peptide degradation: deamidation, oxidation, hydrolysis, aggregation and fibrillation, and how temperature, pH, ionic strength,…

832 questions
bacteriostatic-water
bacteriostatic-water

Water for injection containing roughly 0.9 per cent benzyl alcohol as a bacteriostatic agent. It suppresses growth in a multiple-withdrawal vial;…

112 questions
shelf-life
shelf-life

How long a preparation remains within specification: labelled expiry for a sealed lyophilised vial, beyond-use dating after reconstitution, and…

301 questions
asked by orla_sheridan 14k · 6 months ago
27 votes 3 answers9.9k views
How many draws do I need before a lab trend means anything? My ALT went 24 to 41

Baseline ALT was 24 U/L. Fourteen weeks into semaglutide it came back at 41 U/L, still inside the lab's quoted range of 0 to 50 but a 71% rise from where I started. I…

bloodwork
bloodwork

Laboratory monitoring: which panels are worth ordering, sensible intervals, reference-range versus optimal-range arguments, and how to read a…

284 questions
liver-enzymes
liver-enzymes

ALT, AST, GGT and ALP: what they do and do not indicate about hepatic fat, why enzymes are a poor surrogate for histology, and where non-invasive…

50 questions
dosing-math
dosing-math

The arithmetic itself: milligrams to millilitres to insulin units, concentration after reconstitution, dose per draw, and vial-days per vial. Show…

811 questions
asked by Dr_Signe_Baldursdottir 46k · 14 months ago
27 votes0 answers9.5k views
What is the arithmetic to convert 2.5 mg in 0.5 mL into units on a U-100 scale?

Conditions: 2.5 mg · 0.5 mL. I want the working, not the result — I need to be able to redo it with different numbers. I care about the precision as well as the value…

dosing-math
dosing-math

The arithmetic itself: milligrams to millilitres to insulin units, concentration after reconstitution, dose per draw, and vial-days per vial. Show…

811 questions
insulin-syringe
insulin-syringe

U-100 and U-40 insulin syringes as measuring instruments. A U-100 syringe is graduated in insulin units where 100 units equals 1 mL, so one unit…

268 questions
reconstitution
reconstitution

Taking a lyophilised vial to a solution of known concentration: choice of diluent, volume selection, how to add liquid without shearing the cake,…

330 questions
asked by a_lindgren 46k · 10 months ago
27 votes 3 answers8.8k views
Should I get a baseline serum calcitonin before starting? Working the predictive value

A private clinic offered me a "pre-treatment endocrine screen" including serum calcitonin, with the reasoning that the boxed warning concerns C cells and calcitonin…

thyroid
thyroid

Thyroid questions: the rodent C-cell findings behind the labelled warning, human calcitonin data, TSH drift during weight loss, and the…

14 questions
bloodwork
bloodwork

Laboratory monitoring: which panels are worth ordering, sensible intervals, reference-range versus optimal-range arguments, and how to read a…

284 questions
harm-reduction
harm-reduction

Reducing avoidable risk where a decision has already been made: independent verification before use, sterility practice, dose arithmetic checked…

445 questions
cost-analysis
cost-analysis

Cost arithmetic done honestly: cost per milligram after dead-space loss, list versus net price, comparing a multi-dose vial to a fixed-dose pen,…

261 questions
asked by coldpack_88 37k · 13 months ago
27 votes0 answers8.4k views
What is the most common avoidable mistake in reconstitution?

This is the third vial from the same lot, so I can compare against two known-good ones. I suspect the usual explanation for this is wrong, or at least incomplete. I…

reconstitution
reconstitution

Taking a lyophilised vial to a solution of known concentration: choice of diluent, volume selection, how to add liquid without shearing the cake,…

330 questions
dosing-math
dosing-math

The arithmetic itself: milligrams to millilitres to insulin units, concentration after reconstitution, dose per draw, and vial-days per vial. Show…

811 questions
harm-reduction
harm-reduction

Reducing avoidable risk where a decision has already been made: independent verification before use, sterility practice, dose arithmetic checked…

445 questions
asked by otto_brenner 19k · 17 months ago
27 votes3 answers7.8k views
Should I care about the injection volume on a chromatogram?

I have the report as a PDF with the chromatogram on page two, so I can quote specifics. I would like the mechanism, because I want to be able to reason about the…

hplc
hplc

Reverse-phase high-performance liquid chromatography, the workhorse purity method. Column chemistry, mobile-phase choice, gradient slope,…

466 questions
purity
purity

Purity as chromatographic area per cent - the fraction of detected material that is your target peak. It says nothing about how much material is…

788 questions
reference-standard
reference-standard

Certified reference materials and in-house standards: traceability, the certificate of the standard itself, system suitability, and why every…

179 questions
asked by tobias_reint 19k · 6 months ago
27 votes 5 answers7.6k views
Is an endotoxin test worth paying for on top of a purity figure for a GLP-1 receptor agonist?

Stated plainly: an endotoxin test · a GLP-1 receptor agonist. I would like to set this up properly once, rather than adjust it repeatedly. My budget is real but not…

content-assay
content-assay

Quantified content: how many milligrams of peptide are actually in the vial, measured against a calibrated reference standard. A separate test…

438 questions
batch-testing
batch-testing

Testing at the batch or lot level: sampling plans, how many vials from a lot need testing to say anything about the lot, and the difference…

865 questions
cost-analysis
cost-analysis

Cost arithmetic done honestly: cost per milligram after dead-space loss, list versus net price, comparing a multi-dose vial to a fixed-dose pen,…

261 questions
asked by area_percent 13k · 8 months ago
27 votes0 answers7.5k views
Is SOUL a fair comparison of a GLP-1 receptor agonist against its comparator arm?

What I am working with: SOUL · a GLP-1 receptor agonist. This is asserted often enough that I assumed it was established, and then I went looking for the source. I…

clinical-trials
clinical-trials

Reading the primary literature properly: estimands, intention-to-treat versus per-protocol, confidence intervals, absolute versus relative…

913 questions
semaglutide
semaglutide

A GLP-1 receptor agonist with a fatty-acid-acylated backbone and a roughly one-week half-life, marketed for type 2 diabetes and for weight…

360 questions
tirzepatide
tirzepatide

A dual GIP and GLP-1 receptor agonist. Questions here cover the SURPASS and SURMOUNT programmes, the practical differences from a pure GLP-1…

162 questions
asked by bea_forsberg 14k · 11 months ago
27 votes 3 answers6.9k views
How much of the weight effect is delayed gastric emptying, and is the plateau receptor desensitisation?

Two related mechanism questions I have never seen answered together. First, how much of the weight loss is attributable to delayed gastric emptying as opposed to…

glp1-mechanism
glp1-mechanism

Receptor-level pharmacology: GLP-1R as a class B GPCR, cAMP and PKA signalling, biased agonism, internalisation and resensitisation, and the…

175 questions
plateau
plateau

A stall in progress: distinguishing adaptive thermogenesis from measurement error from adherence drift, how long to observe before changing…

35 questions
gi-side-effects
gi-side-effects

The gastrointestinal cluster as a whole - nausea, vomiting, diarrhoea, constipation, reflux, early satiety - with trial incidence rates, dropout…

416 questions
maintenance-dose
maintenance-dose

Staying put: the lowest dose that holds a result, the difference between the maximum studied dose and the maximum useful dose, and what the…

44 questions
constipation
constipation

Slowed transit as a consequence of delayed gastric emptying and reduced intake: incidence figures, fibre and hydration evidence, and why it often…

14 questions
asked by syringe_ninety 15k · 3 months ago
27 votes 5 answers6.7k views
Is 15 mg in 2 mL of phosphate-buffered diluent a sensible presentation for orforglipron?

The particulars: 15 mg · 2 mL · phosphate-buffered diluent · orforglipron. I would like to define my thresholds before I have a result, for obvious reasons. I want a…

diluent-volume
diluent-volume

Choosing how much diluent to add, which is really a question about what you want your measurement resolution to be. Larger volumes buy you…

308 questions
reconstitution
reconstitution

Taking a lyophilised vial to a solution of known concentration: choice of diluent, volume selection, how to add liquid without shearing the cake,…

330 questions
dosing-math
dosing-math

The arithmetic itself: milligrams to millilitres to insulin units, concentration after reconstitution, dose per draw, and vial-days per vial. Show…

811 questions
asked by imani_dube 19k · 6 months ago
27 votes 5 answers6.6k views
What is the real-world lead time from Nantong to Canada in winter?

What I am working with: Nantong · Canada. I would like help reading this properly rather than being told what conclusion to reach. I have the full report including…

international-shipping
international-shipping

Cross-border movement of research material: transit lanes and their thermal profiles, tracked versus untracked, declaration accuracy, and what…

427 questions
cold-chain
cold-chain

Keeping material within a temperature window from manufacture to use: phase-change packs versus dry ice, thermal mass, transit-lane temperature…

524 questions
customs
customs

Customs handling: how declarations are assessed, why a parcel sits at a facility for a week, seizure notices, and the practical difference between…

186 questions
asked by area_percent 13k · 7 months ago
27 votes0 answers5.5k views
What does ATTAIN-1 actually establish about orforglipron?

Details up front: ATTAIN-1 · orforglipron. This is presented as though it settles something, and I am not convinced it does. I have two documents that appear to…

clinical-trials
clinical-trials

Reading the primary literature properly: estimands, intention-to-treat versus per-protocol, confidence intervals, absolute versus relative…

913 questions
semaglutide
semaglutide

A GLP-1 receptor agonist with a fatty-acid-acylated backbone and a roughly one-week half-life, marketed for type 2 diabetes and for weight…

360 questions
cardiovascular
cardiovascular

Cardiovascular outcomes: the SELECT major-adverse-event result, SOUL, SUSTAIN 6 and REWIND, how to convert a hazard ratio into an absolute risk…

111 questions
asked by ellis_thorne 17k · 6 months ago
27 votes0 answers5.2k views
How comparable are retatrutide and tirzepatide on the evidence available?

What I am working with: retatrutide · tirzepatide. I suspect the honest answer is that it depends, in which case I would like to know on what. Assume I can obtain…

clinical-trials
clinical-trials

Reading the primary literature properly: estimands, intention-to-treat versus per-protocol, confidence intervals, absolute versus relative…

913 questions
semaglutide
semaglutide

A GLP-1 receptor agonist with a fatty-acid-acylated backbone and a roughly one-week half-life, marketed for type 2 diabetes and for weight…

360 questions
tirzepatide
tirzepatide

A dual GIP and GLP-1 receptor agonist. Questions here cover the SURPASS and SURMOUNT programmes, the practical differences from a pure GLP-1…

162 questions
hormones
hormones

Endocrine changes accompanying substantial weight loss: sex hormone binding globulin, testosterone, oestradiol, cortisol and the reproductive…

14 questions
asked by j_wierzbicki 45k · 8 months ago
27 votes0 answers4.5k views
Is an on-chain payment sensible for an order shipping to the United States?

What I am working with: an on-chain payment · the United States. I am trying to build something sustainable rather than something thorough that I will abandon. I have…

payment-privacy
payment-privacy

Payment mechanics and their privacy properties: why suppliers ask for stablecoin transfers, what an on-chain transfer reveals, confirmation…

31 questions
group-buy
group-buy

Pooled purchasing: how the economics work, what trust structure a pool needs, splitting a single tested lot, and the failure modes when the…

41 questions
international-shipping
international-shipping

Cross-border movement of research material: transit lanes and their thermal profiles, tracked versus untracked, declaration accuracy, and what…

427 questions
asked by bridget_nyathi 16k · 6 months ago
26 votes5 answers63k views
What fraction of loss on tirzepatide is lean mass according to STEP 5?

The particulars: tirzepatide · STEP 5. I want to understand what this actually establishes, as opposed to what it is being used to imply. My concern is that I am…

lean-mass
lean-mass

Lean body mass as measured rather than assumed: what DEXA, BIA and air-displacement plethysmography each actually estimate, the body-composition…

164 questions
muscle-loss
muscle-loss

Loss of contractile tissue during energy deficit: what fraction of total loss is lean mass, why the commonly quoted figures are measurement…

82 questions
dexa
dexa

Dual-energy X-ray absorptiometry: what it measures, its precision limits, why hydration state and scan positioning move the numbers, and how to…

84 questions
asked by esther_vandeVelde 49k · 2.3 years ago
26 votes5 answers51k views
What is the arithmetic to convert 15 mg in 2.5 mL into units on a U-100 scale?

The particulars: 15 mg · 2.5 mL. I would like the arithmetic checked rather than the conclusion asserted. I have deliberately not used an online calculator because I…

dosing-math
dosing-math

The arithmetic itself: milligrams to millilitres to insulin units, concentration after reconstitution, dose per draw, and vial-days per vial. Show…

811 questions
insulin-syringe
insulin-syringe

U-100 and U-40 insulin syringes as measuring instruments. A U-100 syringe is graduated in insulin units where 100 units equals 1 mL, so one unit…

268 questions
reconstitution
reconstitution

Taking a lyophilised vial to a solution of known concentration: choice of diluent, volume selection, how to add liquid without shearing the cake,…

330 questions
asked by marta_szymanska 17k · 23 months ago
26 votes 5 answers49k views
Is an MKM order from Xianning likely to hold cold chain to Canada?

For reference: MKM · Xianning · Canada. I would like to define my thresholds before I have a result, for obvious reasons. I want a plan with explicit stopping rules,…

cold-chain
cold-chain

Keeping material within a temperature window from manufacture to use: phase-change packs versus dry ice, thermal mass, transit-lane temperature…

524 questions
international-shipping
international-shipping

Cross-border movement of research material: transit lanes and their thermal profiles, tracked versus untracked, declaration accuracy, and what…

427 questions
vendor-comparison
vendor-comparison

Side-by-side comparison of suppliers on measurable axes - independently confirmed purity and content, lead time, cold-chain handling,…

351 questions
asked by nominal_ten 14k · 2.0 years ago