Mercaptopurine Dosage

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Usual Adult Dose for Intestinal Arterial Insufficiency

Initial Dosage:
Oral: 2.5 mg/kg of body weight per day (100 to 200 mg in the average adult). This dose may be continued daily for several weeks or more in some patients. If, after 4 weeks at this dosage, there is no clinical improvement and no definite evidence of leukocyte or platelet depression, the dosage may be increased up to 5 mg/kg daily. A dosage of 2.5 mg/kg per day may result in a rapid fall in leukocyte count within 1 to 2 weeks in some adults with acute lymphatic leukemia and high total leukocyte counts.

The total daily dosage may be given at one time. It is calculated to the nearest multiple of 25 mg.

Maintenance Therapy: Once a complete hematologic remission is obtained, maintenance therapy is considered essential. A usual daily maintenance dose of mercaptopurine is 1.5 to 2.5 mg/kg per day as a single dose. Mercaptopurine should rarely be relied upon as a single agent for the maintenance of remissions induced in acute leukemia.

Usual Adult Dose for Acute Lymphoblastic Leukemia

Initial Dosage:
Oral: 2.5 mg/kg of body weight per day (100 to 200 mg in the average adult). This dose may be continued daily for several weeks or more in some patients. If, after 4 weeks at this dosage, there is no clinical improvement and no definite evidence of leukocyte or platelet depression, the dosage may be increased up to 5 mg/kg daily. A dosage of 2.5 mg/kg per day may result in a rapid fall in leukocyte count within 1 to 2 weeks in some adults with acute lymphatic leukemia and high total leukocyte counts.

The total daily dosage may be given at one time. It is calculated to the nearest multiple of 25 mg.

Maintenance Therapy: Once a complete hematologic remission is obtained, maintenance therapy is considered essential. A usual daily maintenance dose of mercaptopurine is 1.5 to 2.5 mg/kg per day as a single dose. Mercaptopurine should rarely be relied upon as a single agent for the maintenance of remissions induced in acute leukemia.

Usual Adult Dose for Crohn's Disease - Acute

Oral: 1.0 to 1.5 mg/kg of body weight per day

Usual Adult Dose for Crohn's Disease - Maintenance

Oral: 1.0 to 1.5 mg/kg of body weight per day

Usual Adult Dose for Ulcerative Colitis - Maintenance

Oral: 1.0 to 1.5 mg/kg of body weight per day

Usual Adult Dose for Inflammatory Bowel Disease

Oral: 1.0 to 1.5 mg/kg of body weight per day

Usual Pediatric Dose for Intestinal Arterial Insufficiency

Initial Dosage:
Oral: 2.5 mg/kg of body weight per day (50 mg in an average 5-year-old child). Pediatric patients with acute leukemia have tolerated this dose without difficulty in most cases; it may be continued daily for several weeks or more in some patients. If, after 4 weeks at this dosage, there is no clinical improvement and no definite evidence of leukocyte or platelet depression, the dosage may be increased up to 5 mg/kg daily. A dosage of 2.5 mg/kg per day may result in a rapid fall in leukocyte count within 1 to 2 weeks in some adults with acute lymphatic leukemia and high total leukocyte counts.

The total daily dosage may be given at one time. It is calculated to the nearest multiple of 25 mg.

Maintenance Therapy: Once a complete hematologic remission is obtained, maintenance therapy is considered essential. A usual daily maintenance dose of mercaptopurine is 1.5 to 2.5 mg/kg per day as a single dose. It is to be emphasized that in pediatric patients with acute lymphatic leukemia in remission, superior results have been obtained when mercaptopurine has been combined with other agents (most frequently with methotrexate) for remission maintenance. Mercaptopurine should rarely be relied upon as a single agent for the maintenance of remissions induced in acute leukemia.

Usual Pediatric Dose for Acute Lymphoblastic Leukemia

Initial Dosage:
Oral: 2.5 mg/kg of body weight per day (50 mg in an average 5-year-old child). Pediatric patients with acute leukemia have tolerated this dose without difficulty in most cases; it may be continued daily for several weeks or more in some patients. If, after 4 weeks at this dosage, there is no clinical improvement and no definite evidence of leukocyte or platelet depression, the dosage may be increased up to 5 mg/kg daily. A dosage of 2.5 mg/kg per day may result in a rapid fall in leukocyte count within 1 to 2 weeks in some adults with acute lymphatic leukemia and high total leukocyte counts.

The total daily dosage may be given at one time. It is calculated to the nearest multiple of 25 mg.

Maintenance Therapy: Once a complete hematologic remission is obtained, maintenance therapy is considered essential. A usual daily maintenance dose of mercaptopurine is 1.5 to 2.5 mg/kg per day as a single dose. It is to be emphasized that in pediatric patients with acute lymphatic leukemia in remission, superior results have been obtained when mercaptopurine has been combined with other agents (most frequently with methotrexate) for remission maintenance. Mercaptopurine should rarely be relied upon as a single agent for the maintenance of remissions induced in acute leukemia.

Renal Dose Adjustments

It is probably advisable to start with smaller dosages in patients with impaired renal function, since the latter might result in slower elimination of the drug and metabolites and a greater cumulative effect.

Liver Dose Adjustments

Consideration should be given to reducing the dosage in patients with impaired hepatic function.

Dose Adjustments

The dosage which will be tolerated and be effective varies from patient to patient, and therefore careful titration is necessary to obtain the optimum therapeutic effect without incurring excessive, unintended toxicity.

The dosage of mercaptopurine should be reduced to one third to one quarter of the usual dose if allopurinol is given concurrently.

Because the drug may have a delayed action, it should be discontinued at the first sign of an abnormally large or rapid fall in the leukocyte or platelet count. If subsequently the leukocyte count or platelet count remains constant for 2 or 3 days, or rises, treatment may be resumed.

Precautions

The most frequent, serious, toxic effect of mercaptopurine is myelosuppression resulting in leukopenia, thrombocytopenia, and anemia.

If it is not the intent to deliberately induce bone marrow hypoplasia, it is important to discontinue the drug temporarily at the first evidence of an abnormally large fall in white blood cell count, platelet count, or hemoglobin concentration.

Dialysis

Data not available

Other Comments

Mercaptopurine is a potent drug. It should not be used unless a diagnosis of acute lymphatic leukemia has been adequately established.

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