Not directly active, but undergoes rapid nonenzymatic conversion to the reactive compound 5-(3-methyltriazen-1-y) im-idazole-4-carboxamide (MTIC). The cytotoxic action of MTIC is thought to be due primarily to alkylation of DNA.

Adult anaplastic astrocytoma that has progressed during or after active treatment with a drug regimen containing a nitrosourea and procarbazine.

Spontaneously hydrolyzed at physiologic pH to the active species, MTIC. Rapidly and completely absorbed after oral intake. Mean elimination life: 1.8 hours; eliminated mostly in the urine.

♦ Adult: Initially, 150 mg/m² given once a day for 5 days per 28-day cycle. If the absolute neutrophil count at both the nadir and on the day of dosing (day 29 or day 1 of the next cycle) is >1500 and the platelet count exceeds 100,000, the dose may be increased to 200 mg/m² for another 5 consecutive days. During treatment, obtain CBC on day 22 or within 48 hours of that day and weekly until the absolute neutrophil count is >1500 and the platelet count exceeds 100,000; do not start the next cycle until these counts are reached. If the absolute neutrophil count falls to ≤ 1000 and the platelet count is <50,000 during the cycle, decrease the dose by 50 mg/m², but not below the lowest recommended dose of 100 mg/m².