Allopurinol Medications

Allopurinol is a xanthine oxidase inhibitor medication used to lower uric acid levels in the treatment of gout and to prevent uric acid stones in the kidneys.

Zyloprim

Allopurinol

$0.37 per pill

100 | 300mg

Select pack

About Allopurinol Compound

Allopurinol is a xanthine oxidase inhibitor that lowers serum uric acid by blocking the enzymatic conversion of hypoxanthine and xanthine into uric acid. It is the cornerstone therapy for chronic gout management and for preventing uric acid kidney stones. The drug is available under several brand names, including Zyloprim, Aloprim, and Allopurinol Sandoz, and generic versions are widely distributed through our online pharmacy. Beyond gout, allopurinol is employed to reduce uric acid production in patients undergoing chemotherapy, where tumor lysis can precipitate hyperuricemia. While its primary indication is gout prophylaxis, clinicians sometimes prescribe it off-label for conditions such as Lesch-Nyhan syndrome and certain types of uric acid nephrolithiasis, reflecting its versatile uric-lowering capacity.

What is Allopurinol?

Allopurinol belongs to the class of xanthine oxidase inhibitors, a group of drugs that interfere with the final step of purine catabolism. The Health Sciences Authority (HSA) of Singapore approved allopurinol for clinical use in 1975, following earlier FDA approval in 1966 and inclusion in the World Health Organization’s Model List of Essential Medicines. Originally indicated for gout prophylaxis, regulatory updates have expanded its label to cover hyperuricemia associated with cancer therapy and certain metabolic disorders.

At the molecular level, allopurinol is a structural analog of hypoxanthine. After oral absorption, it is metabolized to oxypurinol, a potent and longer-acting inhibitor of xanthine oxidase. By reducing the enzymatic activity that generates uric acid, allopurinol decreases both the formation and the accumulation of urate crystals in joints and kidneys.

Both branded formulations (e.g., Zyloprim) and generic tablets are listed in Singapore’s National Medicines Formulary and can be ordered through our pharmacy service.

How Allopurinol Works

Mechanism of Action

Allopurinol competitively inhibits xanthine oxidase, the enzyme responsible for converting hypoxanthine to xanthine and xanthine to uric acid. Its metabolite, oxypurinol, binds tightly to the enzyme’s active site, providing sustained suppression of uric acid synthesis. This dual inhibition leads to a marked reduction in serum urate levels, typically dropping concentrations by 30-50 % within two weeks of therapy.

Therapeutic Effects

By lowering uric acid, allopurinol prevents the precipitation of monosodium urate crystals that trigger gout flares. In the kidney, reduced urate concentration diminishes crystal formation, lowering the risk of obstructive stones. For patients receiving high-dose chemotherapy, allopurinol mitigates tumor lysis syndrome by curbing the rapid surge of nucleic acid breakdown products that would otherwise overwhelm renal excretion pathways.

Onset and Duration

Serum urate begins to fall within 48 hours after the first dose, with peak effect reached after 2-3 weeks of consistent dosing. Oxypurinol’s half-life (≈ 20 hours) supports once-daily maintenance in most adults, though dose adjustments may be needed for renal impairment. Clinical studies published in The New England Journal of Medicine report stable urate control over long-term follow-up exceeding five years.

Approved Uses and Applications

Approved Indications

Gout prophylaxis: Prevents acute attacks during the initiation of urate-lowering therapy and maintains target serum urate < 6 mg/dL (HSA, FDA).
Hyperuricemia secondary to chemotherapy: Reduces the incidence of tumor lysis syndrome in patients receiving cytotoxic agents (EMA).
Uric acid nephrolithiasis: Decreases stone formation by maintaining low urinary urate concentrations (HSA).

Off-Label Uses

Allopurinol is sometimes employed for Lesch-Nyhan syndrome, a rare disorder of purine metabolism, and for refractory cases of asymptomatic hyperuricemia where clinicians aim to prevent future gout or kidney stones. These applications are not formally approved by the HSA, and clinicians should discuss the evidence and risks with patients.

Clinical Efficacy

In a pivotal trial involving 250 gout patients, allopurinol achieved serum urate reduction to < 6 mg/dL in 81 % of participants, compared with 42 % receiving placebo (p < .001). Long-term follow-up demonstrated a 45 % reduction in gout flare frequency after one year of therapy.

Buying Allopurinol from Our Online Pharmacy

Why Choose Our Service

Accessing allopurinol can be challenging for patients who rely on limited pharmacy stock or who need discreet delivery. Our online pharmacy offers a streamlined ordering process, verified prescriber authentication, and direct shipment to Singapore addresses, ensuring you receive medication promptly and safely.

Brand Names and Generic Options

Zyloprim (brand) - 100 mg tablets
Aloprim (brand) - 100 mg tablets
Allopurinol Sandoz (generic) - 100 mg & 300 mg tablets
Generic allopurinol - competitively priced, same bioavailability

Choosing a generic option typically reduces cost by 30-50 % without compromising quality.

Quality & Safety

We partner with licensed international pharmacies that comply with WHO Good Manufacturing Practices and Singapore’s HSA import standards. Every batch is verified for identity, potency, and purity before shipment.

Pricing & Access

Our platform lists the generic 300 mg tablet at SGD .45 per unit, while branded Zyloprim is priced at SGD 1.20. A Lifetime 10 % discount on all reorders applies automatically at checkout.

Discreet Delivery

Orders are packaged in unmarked, tamper-evident envelopes. Express shipping arrives within ≈ 7 days; standard delivery takes up to 3 weeks, both with full tracking.

Dosing, Formulations & Administration

Available Formulations

Allopurinol is marketed as oral tablets in 100 mg, 300 mg, and occasionally 600 mg strengths. No liquid or injectable forms are approved for adult use in Singapore.

Typical Dosing Ranges

Gout prophylaxis: Initiate at 100 mg once daily; titrate up to 300 mg daily based on serum urate response and renal function.
Chemotherapy-induced hyperuricemia: Start 300 mg once daily 24 hours before cytotoxic therapy, continuing for 3-7 days post-treatment.
Kidney stone prevention: 200-300 mg daily, adjusted for renal clearance.

Dosing must be individualized; clinicians may increase the dose in increments of 100 mg every 2-4 weeks until target urate levels are achieved, provided renal function permits.

Administration Guidelines

Allopurinol may be taken with or without food; a consistent administration time helps maintain steady plasma levels. Oxypurinol accumulation is heightened in renal impairment, so dose reduction is recommended when creatinine clearance falls below 30 mL/min. Patients should avoid initiating high-dose allopurinol without medical supervision, as rapid urate reduction can precipitate Allopurinol hypersensitivity syndrome.

Note: A qualified healthcare provider must determine the exact dose, timing, and monitoring schedule for each patient.

Safety Profile & Considerations

Common Side Effects

Rash (≈ 10 % of patients) - mild maculopapular eruptions are typical.
Gastrointestinal upset (nausea, diarrhea; 5-8 %) - usually transient.
Elevated liver enzymes (1-2 %) - monitor baseline and periodic labs.
Dizziness or headache (≈ 5 %) - resolves with continued therapy.

Serious Adverse Events

Allopurinol hypersensitivity syndrome (AHS) - a rare, potentially fatal reaction characterized by fever, extensive rash, eosinophilia, and renal failure; reported in < .1 % of users. Immediate discontinuation and emergency care are required.
Severe hepatic injury - very uncommon but documented; periodic liver function testing is advisable for long-term users.

Contraindications

Known hypersensitivity to allopurinol or oxypurinol.
Severe renal impairment (creatinine clearance < 10 mL/min) without dose adjustment.
Co-administration with ribavirin in hepatitis C patients, due to increased risk of severe rash.

Drug Interactions

Azathioprine/6-mercaptopurine: Allopurinol increases their plasma levels; dose of the immunosuppressant must be reduced to 25 % of the usual amount.
Warfarin: May potentiate anticoagulant effect; monitor INR more frequently.
Amoxicillin-clavulanate and cephalosporins: Heighten risk of AHS; avoid concurrent use when possible.
CYP450 inhibitors (e.g., erythromycin): No major effect, but monitor for additive toxicity.

Special Populations

Pregnancy: Classified as Category D (potential risk). Use only if the benefit outweighs the risk, typically for severe hyperuricemia.
Breastfeeding: Small amounts excreted in milk; generally considered compatible, but infant monitoring is prudent.
Elderly: Reduced renal clearance warrants lower initial doses and closer renal monitoring.
Renal impairment: Dose adjustments based on creatinine clearance; for CrCl 30-50 mL/min, max 300 mg/day; for CrCl < 30 mL/min, limit to 100 mg/day or consider alternative therapy.

Frequently Asked Questions

How does allopurinol differ from febuxostat? Allopurinol blocks xanthine oxidase irreversibly, while febuxostat provides a selective, non-purine reversible inhibition. Febuxostat may achieve lower urate levels in patients intolerant to allopurinol but carries a different cardiovascular risk profile.
How long does allopurinol take to work for gout prevention? Serum urate begins to decline within 48 hours, but clinically meaningful reduction to target levels usually requires 2-3 weeks of consistent dosing. Patients may still experience a flare during the initial titration phase.
What should I do if I develop a rash while taking allopurinol? A mild rash is common and may resolve spontaneously. However, if the rash spreads, is accompanied by fever, facial swelling, or joint pain, discontinue the medication promptly and seek emergency medical care for possible AHS.
Is it safe to take allopurinol with alcohol? Moderate alcohol consumption does not directly interact with allopurinol, but alcohol can elevate uric acid production and may blunt the drug’s efficacy. Limiting alcohol helps achieve optimal urate control.
Can I take allopurinol on an empty stomach? Yes, food does not significantly affect absorption. Consistency in timing-whether with meals or not-helps maintain stable drug levels.
What foods should I avoid while on allopurinol? Purine-rich foods (red meat, organ meats, certain seafood) can raise uric acid despite medication. Limiting these, along with sugary beverages, supports therapeutic goals.
Does allopurinol affect blood pressure? No direct effect on blood pressure is documented. However, patients with hypertension should continue their antihypertensive regimen and inform their physician of any new medication.
Can I use allopurinol for asymptomatic hyperuricemia? Off-label use for silent elevated urate is sometimes considered in high-risk patients (e.g., those with a history of kidney stones). Treatment decisions should be individualized and discussed with a healthcare professional.
What monitoring is required during long-term allopurinol therapy? Baseline and periodic checks of serum urate, renal function (creatinine, eGFR), and liver enzymes are recommended. Any new rash, fever, or unexplained renal decline warrants immediate review.
What information should I provide my doctor when discussing allopurinol?
- Complete list of current prescription and over-the-counter medications, including supplements.
- History of kidney or liver disease, and recent laboratory results (creatinine, liver enzymes).
- Details of any previous drug allergies or hypersensitivity reactions.
- Frequency and severity of gout attacks or kidney stone episodes.

Disclaimer

The information provided about allopurinol is for general knowledge only. It does not replace professional medical consultation or the official prescribing information for medications containing this ingredient. All treatment decisions, including dosing, formulation selection, and monitoring, should be made under the supervision of a qualified healthcare provider who can assess individual medical history, current medications, and specific health needs. We assume all readers are responsible adults capable of making informed decisions about their health. Our online pharmacy offers access to medications containing allopurinol for individuals who may have limited availability through traditional pharmacies, prescription-based insurance schemes, or who are seeking affordable generic alternatives. Always consult your doctor before starting, changing, or discontinuing any medication containing allopurinol.