Allopurinol

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Cat Number

API315300

CAS Number

315-30-0

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CAS Number

315-30-0

EINECS

206-250-9

Storage

Store at room temperature

Synonyms

Zyloric; Suspendol; Takanarumin; Allopur; Bloxanth; Uriprim; Xanturat

Molecular Formula

C5H4N4O

Molecular Weight

136.11

Smiles

C1=NNC2=C1C(=O)NC=N2

Appearance

White to off-white solid

Melting Point

350°C

Boiling Point

290.8°C at 760 mmHg

Relative Density

1.89

General Description

Allopurinol is a synthetic xanthine oxidase inhibitor, structurally related to hypoxanthine, with the chemical formula 1H-pyrazolo[3,4-d]pyrimidin-4-ol. It is a white to off-white crystalline powder that is practically insoluble in water. The molecule is a purine analogue that acts as a competitive inhibitor of the enzyme xanthine oxidase.

Mechanism of Action

Allopurinol inhibits the enzyme xanthine oxidase, which is responsible for the conversion of hypoxanthine to xanthine and xanthine to uric acid. By blocking this enzyme, the drug reduces the production of uric acid, lowering serum and urinary urate levels. The active metabolite, oxypurinol, is also a potent inhibitor of xanthine oxidase, contributing to the drug's long duration of action.

Application

Allopurinol is indicated for the management of hyperuricemia in patients with gout, including the prevention of acute gout attacks and the treatment of tophi. It is also used for the prevention of uric acid nephropathy in patients with leukemia and lymphoma undergoing chemotherapy.

In Otsuka Long-Evans Tokushima Fatty rats, high-fructose diet increased body weight, epididymal fat, uric acid, cholesterol, triglycerides, hepatic enzymes, and NAFLD activity score. Allopurinol treatment reduced hepatic steatosis, epididymal fat, serum uric acid, HOMA-IR, and hepatic enzymes. It downregulated lipogenic genes, upregulated lipid oxidation genes, reduced pro-inflammatory cytokines, and decreased ER stress proteins. Allopurinol ameliorates fructose-induced hepatic steatosis through lipid metabolism, inflammation, and ER stress modulation, suggesting a role for uric acid in NAFLD.

Fig. 1 Effects of HFrD and allopurinol treatment on glucose tolerance test. (Cho IJ, et al., 2021)

References

Cho IJ, et al. Allopurinol ameliorates high fructose diet induced hepatic steatosis in diabetic rats through modulation of lipid metabolism, inflammation, and ER stress pathway. Sci Rep. 2021;11(1):9894.

In a phase 2b trial (861 patients with CKD and hyperuricemia), verinurad (a URAT1 inhibitor) combined with allopurinol did not reduce urinary albumin/creatinine ratio or eGFR decline compared to allopurinol alone or placebo at 34 or 60 weeks. Serum urate was dose‑dependently lowered. Adverse events were balanced. Verinurad does not provide renal benefit beyond urate lowering in this population.

Fig. 2 Correlation between change from baseline in UACR and serum urate for the different dose groups. (Heerspink HJL, et al., 2024)

References

Heerspink HJL, et al. Combination Treatment with Verinurad and Allopurinol in CKD: A Randomized Placebo and Active Controlled Trial. J Am Soc Nephrol. 2024;35(5):594-606.

Does Allopurinol require protection from light during long-term storage?

Yes, it is photosensitive. UV exposure can cause photodegradation and discoloration. Store in light-resistant containers, preferably amber glass.

What is the recommended storage temperature for Allopurinol?

Store at controlled room temperature (15–25°C). Avoid excessive heat above 30°C, which can accelerate degradation.

Is Allopurinol stable in tablet and injectable formulations?

Tablets are stable when protected from moisture. Injectable solutions are stable when protected from light and stored at room temperature.

How is the impurity oxypurinol (an oxidative degradation product) monitored?

This degradation product is specifically quantified using a stability-indicating HPLC method, ensuring it remains within pharmacopoeial limits.