Allopurinol
Allopurinol is used to treat gout, high levels of uric acid in the body caused by certain cancer medicines and kidney stones.
Name of drugs:
Allopurinol is widely and easily available over the counter medicine across the world.
Class of drug
Allopurinol is in a class of medications called xanthine oxidase inhibitors.
Use for:
- Allopurinol is used in gout and kidney stones.
- It may also be prescribed if you have some type of cancer treatment causing excessively increased uric acid levels.
- Some treatments can cause a build up of uric acid.
Mechanism of action:
Allopurinol is an xanthine oxidase inhibitor. It works by various mechanisms of action, they are as follows:
- Allopurinol is a structure of the natural purine base hypoxanthine.
- After ingestion allopurinol is metabolized to its active metabolite.
- Oxypurinol (alloxanthin) in the liver, which acts as an inhibitor of xanthine oxidase enzyme.
- This drug is about 90% absorbed from the gastrointestinal tract, peak plasma level normally occurs at 1.5hours and 4.5hours post dose for allopurinol and oxypurinol respectively.
Available as:
tablet
100mg and 300mg.
Powder of injection:
500mg/vial.
Administered as:
Allopurinol is commonly used drugs administered as following routes:
- Oral form is given in the form of tablet’s is 300mg daily for the prevention of recurrent uric acid or calcium nephrolithiasis. Injection is given intravenous routes, allopurinol is 200-400mg/m2 daily single doses or 2 to 3 divided doses.
Pregnancy:
Allopurinol is categorised pregnancy risk C by the FDA as it inhibits purine synthesis and hence may have a direct effect on dividing cells in utero.
Lactation:
If allopurinol is required by the mother it is not a reason to discontinue breastfeeding but exclusively breastfeed infants should be monitored if this drug is used including observation for allergic reactions and periodic CBC and differential blood count.
Elderly:
Allopurinol is the urate lowering drug of choice, but its use in old age is associated with an increased incidence of both cutaneous and severe hypersensitivity reactions.
Liver failure:
Hepatotoxicity, chronic therapy with allopurinol, is associated with transient and minor liver test abnormalities in 2%to6% of patients, which resolve spontaneously or with drug discontinuation.
Kidney failure:
Allopurinol treatment reduces risk of cardiovascular events in 71% compared with standard therapy, conclusion: allopurinol decreases C-reactive protein and slows down the progression of renal disease in patients with chronic kidney disease.
Side effects:
- Numbness.
- Tingling of arms/legs.
- Easy bleeding/bruising.
- Unusual tiredness.
- Sign of kidney problems (such as change in the amount of urine, painful/bloody urination).
- Yellowing eyes/skin.
- Severe stomach / abdominal pain.
- Persistent.
Usual combination:
Zyloprim.
Available common brands:
Zyloprim and alloprim.
Sign of toxicity:
A life threatening toxicity syndrome consisting of
- an erythematous, desquamative skin rash,
- fever,
- hepatitis,
- Eosinophilia and worsening renal function in 78 patients receiving allopurinol is described.
Antidote:
In the management of over doses there is no specific antidote for allopurinol/zyloprim.
Usual drug dose:
Gout:
Mild:
100mg/day PO initially; increased weekly to 200mg to 300mg/day.
Moderate to severe:
100mg/day PO initially, Increased weekly to 400mg to 600mg/day.
Antineoplastic induced hyperuricemia:
PO: 600mg to 800mg/ divided q8-12 hours, starting 1-2 days before chemotherapy. Intravenous: 200mg to 400mg/m2/day; Not to exceed 600mg/m2/day.
