Lab Test Report - Zydus Tablets

I recently completed a lab test on 3 Zydus tablets - all three from the same foil packet. Tablets were purchased from one of the recommended Indian pharmacies here. The average Sirolimus concentration was 0.94 per tablet. The test was about $240 USD.

I’m not an expert on mass spectrometry, so I invite others to review and help understand the analysis.

Chemical Properties:
Chemical Name: Sirolimus
Chemical Formula: C51H79NO13
m/z theoretical: 912.5470
m/z observed: 912.5491
ppm error: 2.3

Expected Concentration
Replicate A: 0.97
Replicate B: 0.95
Replicate C: 0.89
Average: 0.94
Standard Deviation: 0.04

2024_01_18_Sirolimus_Report.pdf (416.4 KB)


Thanks! That’s good to know. Previous tests showed Zydus was around 1.1. So it seems Zydus is ± 10%. For the price, that is acceptable.

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Do they look like the pharmaceutical brand?
Number 21 one side …blank on the opposite?

They are white. Here are some photos.


It seems the overseas / Indian version are different than the US version. The ones I’ve purchased from India all look like the ones above, with 351 printed on them.


Admin, do you know how to interpret the mass spectrometry reading and the other bumps occurring in the sample?

No, I’m more of a business/tech guy, no Mass Spec experience. But - you may be able to understand it better by reading the discussion on the Rapamycin Powder MassSpec analysis done earlier - see here: Sirolimus Powder - 3rd party analysis

Generally I think you want a single strong peak (or dual, if comparing to a “reference” sample of sirolimus (that you have gotten from a “known-good” source (e.g. Sigma Aldrich).


I got a bit more detail from the lab. This gives me some confidence in these tablets.

Those other peaks are most likely isomers of sirolimus. The figures shown are extracted ion chromatograms for sirolimus so these all have the same MW and with further inspection also have the same isotopic distribution as sirolimus. When we look at the pure standard as well (shown in the 1st page of the pdf file above), we also see the same peaks. This is quite common for complex molecules such as sirolimus.


All, in addition to verifying the Sirolimus and amount in the tablets, the lab was also able to identify the other compounds in the Zydus tablets. I don’t know how much was in the tablet. None of these are scary.

This confirms to me the Zydus tablets have the medicine they claim and are safe to take.

• Choline
• Citraconic acid (used in food additives)
• beta-D-Mannopyranose (sugar)
• Citric acid
• Sirolimus

I put these into ChatGPT, and none of these look concerning.

  1. Choline:
  • Chemical Structure: Choline is a quaternary ammonium salt with the chemical formula HOCH2CH2N(��3)3+HOCH2​CH2​N(CH3​)3+​.
  • Safety: Choline is generally safe for consumption when used within recommended doses. It is an essential nutrient involved in various biological processes, including neurotransmitter synthesis and cell membrane structure.
  • Use in Pharmaceuticals: Choline or its derivatives may be used in pharmaceutical formulations for liver health, cognitive support, and as a precursor to acetylcholine. It can also be included to enhance the solubility or bioavailability of certain drugs.
  1. Citraconic Acid:
  • Chemical Structure: Citraconic acid is a cis-alkenedioic acid with the structural formula HOOC-CH=CH-COOHHOOC-CH=CH-COOH.
  • Safety: Citraconic acid is generally recognized as safe when used in accordance with good manufacturing practices. It may be used in certain chemical processes and formulations.
  • Use in Pharmaceuticals: Citraconic acid or its derivatives might be used in pharmaceutical research or manufacturing for specific chemical reactions or as a component in drug formulations.
  1. Beta-D-Mannopyranose:
  • Chemical Structure: Beta-D-Mannopyranose is a monosaccharide, a sugar, with a specific stereochemistry.
  • Safety: Beta-D-Mannopyranose is generally safe for consumption, especially in the context of natural dietary sources. It is a component of various carbohydrates found in fruits and vegetables.
  • Use in Pharmaceuticals: Mannose and its derivatives may be used in pharmaceuticals for various purposes, such as excipients, stabilizers, or even as part of the active pharmaceutical ingredient in some drugs.
  1. Citric Acid:
  • Chemical Structure: Citric acid is a tricarboxylic acid with the chemical formula C6H8O7C6​H8​O7​.
  • Safety: Citric acid is safe for consumption and is widely used in the food and pharmaceutical industries. It occurs naturally in citrus fruits.
  • Use in Pharmaceuticals: Citric acid is commonly used in pharmaceuticals as an acidulant, a buffering agent, or as a stabilizer. It helps adjust the pH of formulations and can enhance the solubility of certain drugs.
  1. Sirolimus:
  • Chemical Structure: Sirolimus is a macrolide compound with immunosuppressive properties.
  • Safety: Sirolimus is a prescription medication and should only be used under the supervision of a healthcare professional. It has known side effects and contraindications.
  • Use in Pharmaceuticals: Sirolimus is used as an immunosuppressive drug, primarily in transplant medicine, to prevent organ transplant rejection. It works by inhibiting the immune system’s response.
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Great to hear. Thanks for posting.

This is of course, consistent with the other tests we’ve had done on tablets:

Here: Rapamycin / Sirolimus from India, Lab Test Report on Quality / Purity

and blood tests checking blood/sirolimus levels: Test results (Biocon Rapacan vs Pfizer Rapamune)

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Yep, it had just been a while so happy to contribute some confidence into the community. Your original post is what inspired me.

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