B. Selegiline

Selegiline , also called deprenyl, selectively inhibits MAO Type B (which metabolizes dopamine) at low to moderate doses but does not inhibit MAO Type A (which metabolizes norepinephrine and serotonin) unless given at above recommended doses, where it loses its selectivity. By, thus, decreasing the metabolism of dopamine, selegiline has been found to increase dopamine levels in the brain. Therefore, it enhances the actions of levodopa when these drugs are administered together. Selegiline substantially reduces the required dose of levodopa. Unlike nonselective MAOIs, selegiline at recommended doses has little potential for causing hypertensive crises. However, if selegiline is administered at high doses, the selectivity of the rug is lost, and the patient is at risk for severe hypertension. Selegiline is metabolized to methamphetamine and amphetamine, whose stimulating properties may produce insomnia if the drug is administered later than midafternoon.