Allopurinol
The hypoxanthine analogue was synthesized as a purine anti-metabolites for cancer chemotherapy, however it had no anti-neoplastic activity, but was a substrate as well as inhibitor of xanthine oxidase.
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| Allopurinol tablet |
allopurinol structure
Allopurinol Formula: C5H4N4O
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| Structure of allopurinol |
allopurinol uses(What is allopurinol used for?)
Uses of allopurinol -
1. Allopurinol is first choice drug in chronic gout it can be used in both over producer and under excretors of uric acid particularly more severe cases with toffee or nephropathy.(allopurinol for gout)
Uricosurics are in frequently used in India and US, they are less effective when GFR is low and are inappropriate in stone formers. The two classes of drugs can also be used together when the body load of urate is large.
2. secondary hyperuricemia due to cancer chemotherapy radiation, thiazides or other drugs; can be controlled by allopurinol, it can even be used prophylatically in these situations.
3. To potentiate 6-mercaptopurine or azathioprine in Cancer chemotherapy and immunosuppressant therapy.
allopurinol side effects(What are the side effects of taking allopurinol?)
Adverse effect of allopurinol -These are uncommon hypersensitivity reaction consisting of races, fever, malaise and muscle pain is most frequent.
It subsides on stopping the drug. Renal impairment increases the incidence of rashes and other reactions to allopurinol.
Steven Johnson Syndrome is a rare but serious risk.
Headache
Nausea
Dizziness - are infrequent; do not need withdrawal
Liver damage is rare.
allopurinol mechanism of action
Allopurinol itself is a short acting competitive inhibitor of xanthine oxidase, but its major metabolite alloxanthine (oxypurine) is a long acting and non competitive inhibitors - primarily responsible for uric acid synthesis inhibition in Vivo.
At high concentration allopurinol also becomes non competitive inhibitors. During allopurinol administration plasma concentration of uric acid is reduced and that of hypoxanthine and xanthine is somewhat increased.
In place of uric acid alone all three Oxypurines are excreted in urine.since xanthine and hypoxanthine are more soluble have a higher renal clearance than that of uric acid and each has its individual solubility, precipitation and crystallization in tissue and urine does not occur.
Because of raised levels of xanthine and hypoxanthine, some feedback inhibition of de novo purine synthesis and reutilization of metabolically derived purine also occurs.
allopurinol drug class
Uric acid synthesis inhibitor -Hypoxanthine analogue
allopurinol dose
Start with 100mg OD,gradually increases as needed to 300mg/day:
Maximum 600mg/day.
is allopurinol an immunosuppressant
Yes,It is used to potentiate 6-mercaptopurine or azathioprine in cancr chemotherapy and immunosuppressant therapy.
Pharmacokinetics of allopuriol
About 80% of orally administered allopurinol is abserved, it is not bound to plasma proteins: metabolized largely to alloxanthine. During chronic medication, it inhibits its own metabolism and about one-third is excreted unchanged, the rest as alloxanthine.
Interaction of allopurinol
1. Allopurinol inhibits the degradation of 6-mercaptopurine and azathiopurine: Their doses should be reduced to one third, but not that of thioguanine, because it follows a different metabolic path.
Probenecid given with allopurinol has Complex interaction, while probenecid shortens half-life of alloxanthine, allopurinol prolongs half-life of probenecid.
Precaution of allopurinol and contraindication of allopurinol -
Liberal fluid intake is advocated during allopurinol therapy, it is contraindicated in hypersensitive patient, during pregnancy and lactation.
It should be cautionaly used in the elderly, children and in patients with kidney or liver disease.
Other questions -
Is allopurinol bad for the kidneys?
Bad for real impaired patient.
Who should not take allopurinol?
Described in precaution segment.
Allopurinol Brand -
Zyloric 100,300mg tablet
Zyloprim
Ciploric 100mg capsule
