indication

For use with other anticancer drugs for the treatment of stage III and stage IV Hodgkin's disease.

pharmacology

Procarbazine is an antineoplastic in the class of alkylating agents and is used to treat various forms of cancer. Alkylating agents are so named because of their ability to add alkyl groups to many electronegative groups under conditions present in cells. They stop tumor growth by cross-linking guanine bases in DNA double-helix strands - directly attacking DNA. This makes the strands unable to uncoil and separate. As this is necessary in DNA replication, the cells can no longer divide. In addition, these drugs add methyl or other alkyl groups onto molecules where they do not belong which in turn inhibits their correct utilization by base pairing and causes a miscoding of DNA. Procarbazine is cell-phase specific for the S phase of cell division.

mechanism of action

The precise mode of cytotoxic action of procarbazine has not been clearly defined. There is evidence that the drug may act by inhibition of protein, RNA and DNA synthesis. Studies have suggested that procarbazine may inhibit transmethylation of methyl groups of methionine into t-RNA. The absence of functional t-RNA could cause the cessation of protein synthesis and consequently DNA and RNA synthesis. In addition, procarbazine may directly damage DNA. Hydrogen peroxide, formed during the auto-oxidation of the drug, may attack protein sulfhydryl groups contained in residual protein which is tightly bound to DNA.

toxicity

LD₅₀=785 mg/kg (orally in rats)

biotransformation

Procarbazine is metabolized primarily in the liver and kidneys. The drug appears to be auto-oxidized to the azo derivative with the release of hydrogen peroxide. The azo derivative isomerizes to the hydrazone, and following hydrolysis splits into a benzylaldehyde derivative and methylhydrazine. The methylhydrazine is further degraded to CO₂ and CH₄ and possibly hydrazine, whereas the aldehyde is oxidized to N-isopropylterephthalamic acid, which is excreted in the urine.

absorption

Procarbazine is rapidly and completely absorbed.

half life

10 minutes

drug interactions

Bezafibrate: MAO Inhibitors may enhance the adverse/toxic effect of Bezafibrate. Avoid concomitant use of bezafibrate with monoamine oxidase inhibitors (MAOIs) like procarbazine.

Brimonidine: MAO Inhibitors like procarbazine may enhance the hypertensive effect of Alpha2-Agonists (Ophthalmic). The concomitant use of monoamine oxidase inhibitors and ophthalmic alpha2 agonists is contraindicated.

Buprenorphine: Buprenorphine may enhance the adverse/toxic effect of MAO Inhibitors like procarbazine. When possible, avoid use of buprenorphine in patients who have used a monoamine oxidase inhibitor within the past 14 days due to possible severe adverse effects.

Desvenlafaxine: Increased risk of serotonin syndrome. Ensure adequate washout period between therapies to avoid toxicity. Concurrent therapy should be avoided.

Digoxin: The antineoplasic agent decreases the effect of digoxin

Methotrexate: Increased nephrotoxicity with this combination

Tetrabenazine: Tetrabenazine may increase the adverse/toxic effects of Procarbazine. Concomitant therapy is contraindicated.

Tolcapone: Tolcapone and Procarbazine decrease the metabolism of endogenous catecholamines. Concomitant therapy may result in increased catecholamine effects. Consider alternate therapy or use cautiously and monitor for increased catecholamine effects.

Tramadol: Tramadol increases the risk of serotonin syndrome and seizure induction by the MAO inhibitor, Procarbazine.

Tranylcypromine: Increased risk of serotonin syndrome. Use caution during concomitant therapy and monitor for symptoms of serotonin syndrome.

Trastuzumab: Trastuzumab may increase the risk of neutropenia and anemia. Monitor closely for signs and symptoms of adverse events.

Trazodone: Increased risk of serotonin syndrome. Monitor for symptoms of serotonin syndrome.

Trimipramine: Increased risk of serotonin syndrome. Ensure adequate washout period between therapies to avoid toxicity. Avoid combination or monitor for symptoms of serotonin syndrome and/or hypertensive crisis.

Venlafaxine: Increased risk of serotonin syndrome. Ensure adequate washout period between therapies to avoid toxicity. Concurrent therapy should be avoided.

Zolmitriptan: The MAO inhibitor, procarbazine, may increase the serum concentration of zolmitriptan by decreasing its metabolism. Concomitant therapy and use of zolmitriptan within two weeks of discontinuing procarbazine are contraindicated.