Procaine has a short duration of action

FIGURE 80 Procaine has a short duration of action. Because it causes vasodilation, a vasoconstricting substance is added to the procaine solution to delay systemic absorption. 

Procarbazine may inhibit transmethylation of methyl groups of methionine into tRNA. The absence of functional tRNA 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 autooxidation of the drug, may attack protein sulfhydryl groups contained in residual protein that is tightly bound to DNA. 

Procarbazine is rapidly and completely absorbed from the GI tract and quickly equilibrates between plasma and CSF. Peak CSF levels occur in 30 to 90 minutes. Following oral administration, maximum peak plasma concentrations occur within 60 minutes. 

Procarbazine is metabolized in the liver to cytotoxic products. The major portion of drug is excreted in the urine as V-isopropylterephthalamic acid (approximately 70% within 24 hours following oral and IV administration). Less than 5% is excreted in urine unchanged. 

After IV injection, the plasma half-life is approximately 10 minutes. Procarbazine crosses the blood-brain barrier. 

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