PeptideStack
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Unanswered questions

Questions with no answer at all. Not questions with no accepted answer — those are elsewhere.

741 questions · page 3 of 31

17 votes0 answers5.8k views
When does dizziness stop being a tolerability issue and become a clinical one?

I have certificates from two lots and an independent result on one of them. I would rather over-plan the first cycle and simplify later. I am prepared to do the work…

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
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
pancreatitis
pancreatitis

Acute pancreatitis as a labelled risk: background incidence, the signal in pooled trial and pharmacovigilance data, lipase interpretation, and the…

14 questions
asked by k_szabo 45k · 2 months ago
5 votes0 answers1.9k views
How do I compute the +4 charge state m/z for a peptide of 4113.6 Da?

The particulars: +4 · 4113.6 Da. I would like the arithmetic checked rather than the conclusion asserted. I have deliberately not used an online calculator because I…

mass-spec
mass-spec

Mass spectrometry for identity confirmation: electrospray ionisation, multiple charge states, monoisotopic versus average mass, deconvolution, and…

38 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
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 jonas_ekstrom 18k · 2 months ago
19 votes0 answers2.5k views
Has anyone independently verified an MKM ecnoglutide batch COA?

The particulars: MKM · ecnoglutide. I would like to know whether this claim survives contact with evidence. If the answer is "nobody has tested that", I would like…

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
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
asked by tabular_nums 47k · 2 months ago
21 votes0 answers4.5k views
How does mazdutide at 2.5 mg weekly compare on cost per milligram across routes?

Details up front: mazdutide · 2.5 mg. This should be a straightforward calculation and I keep getting two different answers. The numbers are arbitrary; the method is…

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
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
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 seamus_brady 17k · 2 months ago
22 votes0 answers6.7k views
Does a large published testing history at JEEP imply lot consistency?

I have the report as a PDF with the chromatogram on page two, so I can quote specifics. I can predict the outcome but I cannot explain it, which means I will get the…

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
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
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
asked by tyndall_haze 48k · 2 months ago
12 votes0 answers1.6k views
How do I write up a result so it is useful to someone else?

I have the report as a PDF with the chromatogram on page two, so I can quote specifics. I would like to understand the steps well enough to explain them to someone…

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
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
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 sasha_ferreira 15k · 3 months ago
12 votes0 answers3.2k views
How much of the gross mass of a 30 mg orforglipron vial is actually peptide?

What I have: 30 mg · orforglipron. I can do the algebra. I am not confident about the conversion factors. If there is a standard way to lay this out, I would rather…

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
water-content
water-content

Residual moisture in a lyophilised solid, measured by Karl Fischer titration or loss on drying. It drives both the mass balance on a content assay…

39 questions
acetate-content
acetate-content

Counter-ion content, most often acetate or trifluoroacetate, and why it matters: the counter-ion and residual water are part of the gross mass you…

87 questions
asked by p_mkhize 41k · 3 months ago
16 votes0 answers2.6k views
Does hair thinning at week eight of orforglipron usually resolve without a dose change?

Concretely: hair thinning · eight · orforglipron. I am trying to do this correctly the first time rather than learn it by getting it wrong. I have already made one…

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
titration
titration

Stepwise dose increases over weeks, why the label schedules exist at all, and what tolerability-driven deviation from a schedule looks like in…

444 questions
nausea
nausea

The dominant tolerability signal in every trial of the class: incidence, timing relative to a dose step, duration, and the distinction between…

346 questions
asked by gel_pack_warm 13k · 3 months ago
2 votes0 answers931 views
What does the mechanism of mazdutide predict that SELECT did not test?

Numbers first: mazdutide · SELECT. I can predict the outcome but I cannot explain it, which means I will get the next case wrong. I would like to know how confident…

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
clinical-trials
clinical-trials

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

913 questions
gip-receptor
gip-receptor

GIP receptor pharmacology, and the still-unsettled question of whether agonism or antagonism at GIPR is the metabolically useful direction.…

83 questions
asked by fiadh_cronin 14k · 3 months ago
21 votes0 answers6k views
Does retatrutide adsorb measurably to the vial wall at 3.33 mg/mL?

Setup, so nobody has to ask: retatrutide · 3.33 mg/mL. I have worked this out and I would like someone to find the error, because I suspect there is one. My working…

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
storage
storage

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

646 questions
asked by grainne_ahearn 13k · 3 months ago
1 vote0 answers294 views
Is 2.5 mg/mL a sensible working concentration for a GLP-1 receptor agonist, or should I go lower?

What I am working with: 2.5 mg/mL · a GLP-1 receptor agonist. Both of these get recommended confidently by different people, which suggests neither is obviously…

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 Dr_Marek_Zielinski 39k · 3 months ago
6 votes0 answers2.5k views
What would make you reject a Homopeptide vial on visual inspection alone?

For context, I am working with a 10 mg presentation and a 2 mL fill. I want to decide this in advance so that I am not deciding it under pressure later. Assume I will…

vial-inspection
vial-inspection

What you can learn by looking: cake morphology, meniscus films, fibres versus stopper fragments versus true particulates, clarity after…

66 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
sterility
sterility

Sterility as a test result rather than an adjective. Covers what a sterility test actually measures, why "sterile filtered" on a document is close…

122 questions
asked by Dr_Signe_Baldursdottir 46k · 3 months ago
6 votes0 answers1.9k views
What is the real-world lead time from Xianning to Norway in winter?

The case in front of me: Xianning · Norway. The figures are clear enough; the question is what they mean and what they do not. I can supply the numbers if the…

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 seamus_brady 17k · 3 months ago
23 votes0 answers3.3k views
If I add 2 mL of BAC water to a 10 mg vial, how many units is a 0.5 mg dose?

My setup is a refrigerator with a logger and a small work area I wipe down, nothing more. I want the working, not the result — I need to be able to redo it with…

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
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
asked by rota_site 55k · 3 months ago
16 votes0 answers5.1k views
How many units on a 1 mL luer-lock syringe is a 20 mg dose at 5 mg/mL?

The particulars: a 1 mL luer-lock syringe · 20 mg · 5 mg/mL. I would like the arithmetic checked rather than the conclusion asserted. I have deliberately not used an…

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 imani_dube 19k · 3 months ago
15 votes0 answers5k views
Would you re-test ecnoglutide after four weeks at 4 °C, or accept the original certificate?

The case in front of me: ecnoglutide · four weeks · 4 °C. The failure mode I am trying to avoid is making this decision emotionally. I have twelve months in view and…

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
peptide-stability
peptide-stability

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

832 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 tare_weight 47k · 3 months ago
23 votes0 answers6k views
What happens to oral semaglutide after ten weeks at 2–8 °C in solution?

For reference: oral semaglutide · ten weeks · 2–8 °C. I would like the mechanism, because I want to be able to reason about the cases nobody has written about. I have…

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
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 halvard_ness 42k · 3 months ago
18 votes0 answers5.4k views
Is ERP worth the price difference against Shanghai Sigma-Audley on measured results?

Stated plainly: ERP · Shanghai Sigma-Audley. Both of these get recommended confidently by different people, which suggests neither is obviously right. My constraints…

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
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
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
asked by s_kalniete 47k · 3 months ago
1 vote0 answers266 views
Does a formic acid mobile phase change the purity number I get for mazdutide on a wide-pore C18 column?

Setup, so nobody has to ask: a formic acid mobile phase · mazdutide · a wide-pore C18 column. The empirical answer seems settled. The explanation does not. If 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 mala_venkatesh 21k · 3 months ago
24 votes0 answers9.5k views
How comparable are mazdutide and cagrilintide on the evidence available?

Numbers first: mazdutide · cagrilintide. I want to know what the trade-off actually is rather than which option is fashionable. I would rather have a defensible…

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 oona_kekkonen 16k · 3 months ago
7 votes0 answers3.2k views
Why do two papers on FLOW report different headline figures?

I have the full paper rather than the abstract, and the supplementary appendix. I would like the mechanism, because I want to be able to reason about the cases nobody…

clinical-trials
clinical-trials

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

913 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
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
asked by v_ramaswamy 40k · 3 months ago
2 votes0 answers693 views
Would you accept 99.4% on orforglipron from GGPeps without a content assay?

What I have: 99.4% · orforglipron · GGPeps. I would rather over-plan the first cycle and simplify later. I am prepared to do the work if someone can tell me which…

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
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
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
asked by nynke_dekker 18k · 3 months ago
17 votes0 answers5.6k views
What does a 98.8% purity with a lot-specific certificate attached let me conclude?

Details up front: 98.8% · lot-specific certificate. This is presented as though it settles something, and I am not convinced it does. I have two documents that appear…

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
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
hplc
hplc

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

466 questions
asked by Dr_Malik_Osei 37k · 3 months ago
22 votes0 answers8.8k views
What is the dead-space loss per draw with a 18G drawing needle at 1 mg/mL?

For reference: an 18G drawing needle · 1 mg/mL. I would like the arithmetic checked rather than the conclusion asserted. I have deliberately not used an online…

dead-space
dead-space

The volume trapped in the syringe hub and needle after the plunger bottoms out. It is small in absolute terms and large as a fraction of a small…

110 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
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 RP_C18 85k · 3 months ago