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Unanswered questions

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

739 questions · page 12 of 31

15 votes0 answers3.9k views
If I reconstitute a 20 mg vial with 3 mL of bacteriostatic water, what concentration do I end up with?

What I am working with: 20 mg · 3 mL · bacteriostatic water. I have worked this out and I would like someone to find the error, because I suspect there is one. My…

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,…

313 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…

295 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…

764 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;…

149 questions
asked by ruaidhri_o_shea 25k · 10 months ago
21 votes0 answers9.8k views
How much fluid is enough when thirst cues are blunted?

The trend is what I care about; individual weeks are obviously noise. I would like to understand the steps well enough to explain them to someone else. I have access…

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
electrolytes
electrolytes

Sodium, potassium and magnesium during reduced intake and GI losses: what the symptoms of a shortfall look like, when a panel is worth drawing,…

72 questions
kidney-function
kidney-function

eGFR, creatinine, cystatin C and albuminuria: the acute haemodynamic dip that is not injury, the renal outcome data from the FLOW programme, and…

141 questions
asked by Dr_Malik_Osei 19k · 10 months ago
28 votes0 answers14k views
Is a 95.2% result from Janoshik comparable to 97.6% from Medutest?

Details up front: 95.2% · Janoshik · 97.6% · Medutest. I have used one of these for a while and I am considering switching, which requires a reason. What I care about…

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…

833 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…

910 questions
reference-standard
reference-standard

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

185 questions
janoshik
janoshik

Janoshik Analytical, an independent third-party testing laboratory widely used by this community for HPLC purity, identity and quantified content…

139 questions
medutest
medutest

Medutest, one of four independent testing and verification services referenced throughout this site. Use this tag for its methods, its report…

126 questions
asked by tyndall_haze 38k · 10 months ago
21 votes0 answers9.7k views
Would you accept 98.2% on liraglutide from ERP without a content assay?

The case in front of me: 98.2% · liraglutide · ERP. I want to decide this in advance so that I am not deciding it under pressure later. Assume I will follow the plan…

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…

833 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…

476 questions
vendor-vetting
vendor-vetting

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

454 questions
liraglutide
liraglutide

A once-daily GLP-1 receptor agonist and the compound that established the class. Still relevant for its shorter half-life, its paediatric and…

235 questions
asked by shear_at_the_front 17k · 10 months ago
20 votes0 answers6.9k views
What does TRIUMPH-3 tell me about early satiety at the 4 mg dose?

The specifics, since they change the answer: TRIUMPH-3 · early satiety · 4 mg. I have the document in front of me and I can read the numbers. What I cannot do is…

clinical-trials
clinical-trials

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

745 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…

162 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…

456 questions
asked by kofi_mensah 18k · 10 months ago
28 votes0 answers6.9k views
Is 95.2% a realistic purity ceiling for retatrutide given its chain length?

Numbers first: 95.2% · retatrutide. This should be a straightforward calculation and I keep getting two different answers. The numbers are arbitrary; the method is…

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…

833 questions
hplc
hplc

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

503 questions
peptide-mapping
peptide-mapping

Enzymatic digestion followed by LC-MS/MS to confirm sequence rather than just mass. The method that catches a scrambled sequence or a D-amino-acid…

103 questions
retatrutide
retatrutide

An investigational GLP-1, GIP and glucagon receptor tri-agonist, studied in the TRIUMPH programme. Not approved anywhere. Use this tag for…

251 questions
asked by net_peptide 12k · 10 months ago
16 votes0 answers8.2k views
Is a 25G drawing needle the right choice for drawing tirzepatide at 4 mg/mL?

Conditions: a 25G drawing needle · tirzepatide · 4 mg/mL. I would like the axes of comparison first and the recommendation second. I have tried the first option and…

needle-gauge
needle-gauge

Gauge and length selection, the trade-off between draw time and tissue trauma, coring risk with larger-bore needles, and why a fixed-needle…

91 questions
injection-technique
injection-technique

Technique questions: angle, pinch versus flat, aspiration, injection speed, air bubbles, and the handling steps that determine whether you deliver…

96 questions
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…

117 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…

370 questions
asked by helena_vidmar 8.5k · 10 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…

764 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…

244 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,…

313 questions
asked by a_lindgren 58k · 10 months ago
31 votes0 answers8.6k views
How many freeze-thaw cycles will ecnoglutide at 2 mg/mL tolerate?

The case in front of me: ecnoglutide · 2 mg/mL. I am trying to do this correctly the first time rather than learn it by getting it wrong. I have already made one…

freeze-thaw
freeze-thaw

What repeated freezing does to a peptide in solution: ice-crystal shear at the growing front, freeze-concentration of solutes, pH shifts as buffer…

57 questions
peptide-stability
peptide-stability

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

908 questions
storage
storage

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

701 questions
ecnoglutide
ecnoglutide

A long-acting GLP-1 receptor agonist with a cAMP-biased signalling profile. A niche tag, mostly used for mechanism questions about biased agonism…

223 questions
asked by kofi_mensah 18k · 10 months ago
21 votes0 answers7.1k views
Would you accept 98.2% on mazdutide from QST without a content assay?

Stated plainly: 98.2% · mazdutide · QST. I am trying to build something sustainable rather than something thorough that I will abandon. I have already decided the…

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…

833 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…

476 questions
vendor-vetting
vendor-vetting

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

454 questions
mazdutide
mazdutide

A GLP-1 and glucagon receptor dual agonist developed primarily in China, with a distinct dose range and a fast-moving publication record.…

237 questions
asked by Dr_Jonas_Halvorsen 28k · 10 months ago
16 votes0 answers9.8k views
Does headache at week two of survodutide usually resolve without a dose change?

Details up front: headache · two · survodutide. Everything I have found on this is either a forum aside or a product page, neither of which I trust. I am comfortable…

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…

456 questions
harm-reduction
harm-reduction

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

472 questions
survodutide
survodutide

A GLP-1 and glucagon receptor dual agonist with a substantial published MASH dataset. Use this tag for its hepatic endpoints, its dose ladder, and…

225 questions
asked by h_pergande 71k · 10 months ago
19 votes0 answers10k views
What is the arithmetic to convert 2.5 mg in 1.5 mL into units on a U-100 scale?

Conditions: 2.5 mg · 1.5 mL. Please show the division. I want to check my own against yours. I would like the general form as well as the specific number, so I can…

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…

764 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…

244 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,…

313 questions
asked by pascal_thibault 11k · 10 months ago
21 votes0 answers4.8k views
Does hair thinning at week four of survodutide usually resolve without a dose change?

Details up front: hair thinning · four · survodutide. This is a procedural question rather than a theoretical one, and I would like the procedure rather than the…

hair-loss
hair-loss

Telogen effluvium following rapid weight loss versus a drug-attributable effect: the timing signature that distinguishes them, protein and…

50 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…

456 questions
survodutide
survodutide

A GLP-1 and glucagon receptor dual agonist with a substantial published MASH dataset. Use this tag for its hepatic endpoints, its dose ladder, and…

225 questions
asked by tare_weight 60k · 10 months ago
27 votes0 answers21k views
What has PeptideMeter published on HJ lots in the last year?

The specifics, since they change the answer: PeptideMeter · HJ. I have the document in front of me and I can read the numbers. What I cannot do is interpret them. I…

vendor-investigate
vendor-investigate

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

113 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…

910 questions
vendor-comparison
vendor-comparison

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

388 questions
peptidemeter
peptidemeter

PeptideMeter, an independent peptide analytics and vendor-rating service. Use this tag for its published datasets, its rating methodology, and how…

107 questions
asked by lukas_sedlacek 16k · 11 months ago
24 votes0 answers10k views
Can I reconstitute oral semaglutide at 4 mg/mL and still measure a small dose accurately?

For reference: oral semaglutide · 4 mg/mL. I am at the decision point and I would rather think it through than improvise. I would rather spend money on measurement…

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…

295 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…

244 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…

764 questions
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…

219 questions
asked by nils_karlberg 9.4k · 11 months ago
13 votes0 answers6.8k views
My tirzepatide vial sat at 37 °C for fourteen days — is testing worth it before use?

For reference: tirzepatide · 37 °C · fourteen days. I am at the decision point and I would rather think it through than improvise. I would rather spend money on…

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…

578 questions
peptide-stability
peptide-stability

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

908 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…

910 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…

370 questions
asked by pascal_thibault 11k · 11 months ago
6 votes0 answers4.8k views
What does a 503A pharmacy need to prepare orforglipron lawfully?

This is a United States plan; I appreciate the answer is jurisdiction-specific. I have read the primary source rather than the summary, which has left me with more…

pharmacy-503a
pharmacy-503a

Section 503A traditional compounding pharmacies specifically: patient-specific prescriptions, accreditation such as PCAB and ACHC, USP 797…

17 questions
compounding
compounding

Compounded preparations: what a 503A and a 503B facility may legally prepare and when, base versus salt forms, beyond-use dating under USP…

61 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…

771 questions
orforglipron
orforglipron

A non-peptide, orally bioavailable small-molecule GLP-1 receptor agonist studied in the ATTAIN programme. It is not a peptide, which changes…

219 questions
asked by second_lot 9.4k · 11 months ago
12 votes0 answers3.4k views
Can I re-freeze a lyophilised vial that reached room temperature in transit?

This is a recurring problem with one particular shipping lane rather than a one-off. Everything I have found on this is either a forum aside or a product page,…

freeze-thaw
freeze-thaw

What repeated freezing does to a peptide in solution: ice-crystal shear at the growing front, freeze-concentration of solutes, pH shifts as buffer…

57 questions
storage
storage

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

701 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…

578 questions
asked by lucia_marchetti 19k · 11 months ago
2 votes0 answers2.4k views
Is 2.4 mg weekly a defensible maintenance dose for mazdutide?

Stated plainly: 2.4 mg · mazdutide. I am trying to build something sustainable rather than something thorough that I will abandon. I have already decided the broad…

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…

54 questions
clinical-trials
clinical-trials

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

745 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…

764 questions
mazdutide
mazdutide

A GLP-1 and glucagon receptor dual agonist developed primarily in China, with a distinct dose range and a fast-moving publication record.…

237 questions
asked by ben_akintola 10k · 11 months ago
7 votes0 answers4.1k views
Is injection-site erythema on dulaglutide dose-dependent or dose-rate dependent?

What I am working with: injection-site erythema · dulaglutide. I can predict the outcome but I cannot explain it, which means I will get the next case wrong. I would…

injection-site-reaction
injection-site-reaction

Local reactions: erythema, induration, pruritus and nodules. Their relationship to injection depth, diluent composition, benzyl alcohol…

49 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…

456 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…

200 questions
asked by juliette_farnese 13k · 11 months ago
18 votes0 answers6.7k views
Is resistance training nine times a week enough at 900 kcal a day?

Concretely: nine · 900 kcal. The failure mode I am trying to avoid is making this decision emotionally. I have twelve months in view and I would like the plan to…

resistance-training
resistance-training

Loaded training as the primary intervention for retaining lean mass in a deficit: minimum effective dose, frequency versus volume, and why…

43 questions
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…

127 questions
exercise
exercise

Training during substantial weight loss: cardiorespiratory work, step count, low energy availability, and how exercise interacts with the appetite…

38 questions
asked by ravi_pillai 12k · 11 months ago
18 votes0 answers10k views
Do the cardiovascular benefits depend on the weight loss?

This is a question about interpretation, not about whether to act — I will take action questions elsewhere. I want to know whether this is a real physical effect or…

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…

68 questions
clinical-trials
clinical-trials

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

745 questions
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…

139 questions
asked by Dr_Wren_Halliday 19k · 11 months ago
19 votes0 answers11k views
Is survodutide at 5 mg/mL stable enough for ten weeks of multi-withdrawal use?

Concretely: survodutide · 5 mg/mL · ten weeks. The claim is plausible, which is exactly why I want to check it. I am able to read a paper if someone points me at one.…

peptide-stability
peptide-stability

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

908 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;…

149 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…

327 questions
survodutide
survodutide

A GLP-1 and glucagon receptor dual agonist with a substantial published MASH dataset. Use this tag for its hepatic endpoints, its dose ladder, and…

225 questions
asked by one_ml_bac 18k · 11 months ago
17 votes0 answers13k views
How many vial-days does a 4 mg vial give at 6.67 mg/mL on a weekly schedule?

For reference: 4 mg · 6.67 mg/mL. I would rather understand the derivation than memorise the outcome. Two people I asked gave two answers that differ by a factor of…

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…

764 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,…

260 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…

295 questions
asked by tadhg_o_riordan 7.7k · 11 months ago