Albendazole (CAS 54965-21-8) is a benzimidazole anthelmintic supplied as an active pharmaceutical ingredient in a human-grade specification (USP, with an EP option) and in a separate veterinary specification. The two are not the same material graded differently – they carry different test sets, and the differences matter to the buyer. Both grades are supplied as a white to slightly yellowish powder micronised to a defined particle size.
Human grade – USP specification
| Parameter | Limit | Why it is on the specification |
|---|---|---|
| Description | White or slightly yellowish powder | Colour is the first visible sign of oxidation |
| Identification A | IR spectrum concordant with Albendazole CRS or WS | Confirms identity against the reference standard |
| Identification B | Retention time of the major peak matches the standard, as obtained in the assay | Orthogonal confirmation by liquid chromatography |
| Albendazole oxide and albendazole sulfone | Max 0.4% | Oxidative degradation products; the sulfoxide is also the active metabolite, so the limit protects both stability and the impurity story |
| Fenbendazole related compound A | Max 0.23% | Structurally related process impurity from the benzimidazole route |
| Albendazole related compound A | Max 0.15% | Defined process impurity |
| Albendazole related compound F | Max 0.5% | Defined process impurity with the widest single limit in the set |
| Fenbendazole related compound B | Max 0.15% | As above |
| Albendazole ethyl carbamate (if present) | Max 0.15% | A carbamate with a potential genotoxicity concern – controlled as a specific impurity rather than relying on the unspecified limit |
| Any unspecified impurity | Max 0.10% | The reporting and qualification gate for everything not named |
| Total impurities | Max 0.8% | Summed profile |
| Loss on drying | Max 0.5% | Moisture drives hydrolysis and assay drift |
| Residue on ignition | Max 0.2% | Inorganic residue |
| Residual solvents – methanol | Max 3000 ppm | ICH Q3C Class 2 limit for methanol |
| Residual solvents – toluene | Max 890 ppm | ICH Q3C Class 2 limit for toluene |
| Assay | 98.0 – 102.0% | Two-sided window |
| Particle size | D90 max 20 micrometre; not less than 90% below 20 micrometre | Dissolution-limiting property – see the particle size page for why |
A European Pharmacopoeia (EP 12.3) specification is also available; the detailed parameter set is issued on request because the EP impurity nomenclature differs from the USP one and the two should be compared item by item before a bid is placed.
Veterinary grade specification
| Parameter | Limit | What it tells you |
|---|---|---|
| Related substances | Max 1.0% | A wider total-impurity window than the human grade, with no named individual impurities |
| Loss on drying | Max 0.5% | Same as the human grade |
| Sulphated ash | Max 0.2% | Equivalent to residue on ignition in the human specification |
| Iron salt | Max 0.003% | A test that does not appear on the human specification at all – iron matters in feed and drinking-water applications |
| Assay | Min 98.5% | Single-sided: no upper limit, because there is no formulated-dose argument to protect |
| Particle size | 90% below 20 micrometre | Same practical target as the human grade – micronisation is not a grades differentiator |
The three differences that actually separate the grades
| Point | Human (USP/EP) | Veterinary |
|---|---|---|
| Named impurities | Six named related compounds plus unspecified and total limits | No named compounds – only a total limit |
| Genotoxic impurity | Albendazole ethyl carbamate controlled at 0.15% if present | Not tested |
| Residual solvents | Methanol and toluene to ICH Q3C limits | Not tested |
| Iron salt | Not tested | Max 0.003% |
| Assay window | 98.0 – 102.0%, both sides controlled | Min 98.5%, no upper limit |
The practical consequence: a veterinary lot cannot be released against the human specification and vice versa, even though both are the same molecule at similar assay. Buying decisions should be made on the end use, not on which grade happens to be in stock.
Typical applications
- Human medicine – benzimidazole anthelmintic used against intestinal nematodes and in the longer-course treatment of tissue-dwelling larval infections.
- Veterinary medicine – broad-spectrum anthelmintic for cattle, sheep, goats, swine, horses and companion animals, in bolus, drench, premix and oral suspension forms.
- Formulation inputs – micronised API for tablets, chewables and suspension concentrates, where particle size drives the dissolution step.
Packaging, storage and documentation
| Item | Detail |
|---|---|
| Packaging | 25 kg fibre drums with double PE liner; smaller packs on request |
| Storage | Cool, dry, protected from light. The molecule is oxidation- and light-sensitive; keep containers sealed and away from humidity |
| Documentation | Batch COA against the specification ordered (USP, EP or veterinary), plus SDS; residual solvent and particle size data on request |
| Regulatory | Confirm TSCA and REACH status for CAS 54965-21-8 on enquiry; the grade statement and the market of use determine what your customer’s audit will require |
For the technical background and the grade comparison in detail, see the albendazole technical guide, and the human versus veterinary grade comparison.
