Adults

For newly diagnosed glioblastoma: Initial phase (concomitant with radiotherapy) 75 mg/m² daily for 42 days. Maintenance phase (after radiotherapy) 150 mg/m² once daily for 5 days, repeated every 28 days for 6 cycles. For refractory anaplastic astrocytoma: Initially 150 mg/m² once daily for 5 days, repeated every 28 days. May increase to 200 mg/m² if tolerated.

Elderly

No specific dose adjustments needed for elderly patients, but monitor carefully for myelosuppression and other adverse effects.

Renal_impairment

Use with caution in patients with severe renal impairment. No specific dose adjustment recommended for mild to moderate renal impairment, but careful monitoring is advised.

Onset

Not typically defined for chemotherapy agents; effects are cumulative over cycles.

Excretion

Primarily excreted renally (5-10% as unchanged drug, the rest as metabolites) within 24 hours. A small amount is eliminated via feces.

Half life

Approximately 1.8 hours (plasma elimination half-life).

Absorption

Rapidly and almost completely absorbed after oral administration, with peak plasma concentrations occurring 0.5-1.5 hours post-dose. Bioavailability is approximately 100%.

Metabolism

Spontaneously hydrolyzed at physiological pH to the active metabolite MTIC, which is then further metabolized.

Valproic acid

Concomitant use with valproic acid may lead to a small but statistically significant decrease in temozolomide clearance, potentially increasing exposure.

Other myelosuppressive agents

Increased risk of myelosuppression when co-administered with other agents that cause bone marrow suppression.