<prompt> All drugs are metabolized by acetylation EXCEPT:PhenytoinIsoniazidProcainamideHydralazine  <response>: Ans. a PhenytoinRef. KDT 125; katzung 11th ed. 80ACETYLATION Compounds having amino or hydralazine residues are conjugated with the help of N-Acetyl transferase enzyme. If acetylation is slow- its toxic Fast acetylation- not effective or effectiveness decreases Normal acetylation- effective These drugs are remembered as SHIP drugs: Sulfonamides dapsone Hydralazine anti HTN Isoniazid anti TB Procainamide anti-arrhythmic NOTE- phenytoin is an anti epileptic drug, which is always confused with procainamide in SHIP drugs. Phenytoin doesnt come under SHIP drugs. Phenytoin hydroxylation in liver is carried out by cytochrome P 450. SHIP drugs causes SLE. 