All the following Antiepileptics are inducers except-

Ans. is 'a' i.e., Valproate o Ketoconazole is a P-450 system inhibitor.Drug metabolizing enzvmeso The drug metabolizing enzymes are divided into two types :1. Microsomalo These are located on smooth endoplasmic reticulum primarily in liver, also in kidney, intestinal mucosa an lungs.o Examples are monooxygenase, cytochrome P450, glucronyl transferase,o They catalyze most of the oxidation, reduction, hydrolysis and glucuronide conjugation,o They are inducible by drugs, diet and other agencies.2 Non microsomalo These are present in the cytoplasm and mitochondria of hepatic cells as well as in other tissues including plasma.o Examples are flavoprotein oxidase, esterases, amidases and conjugases.o They catalyze some oxidation and reduction, many hydrolysis and all conjugation except glucuronidation.o They are not inducible but many show genetic polymorphism (acetyl transferase, pseudocholinesterase).Drugs that induce microsomal enzymeso Phenobarbitoneo CarbamezepineoPhenytoino Omeprazoleo Rifampino Clofibrateo Glucocorticoidso Meprobamateo Isoniazido Ritonaviro Chloral hydrateo Glutethimideo Phenylbutazoneo Chronic alcohol intakeo Griseofulvino Cigarette smokingo DDTo Cyclophosphamide Remembero All Barbiturates are enzyme inducers except secobarbital, which inhibits the enzyme,o Acutely, ritonavir is an inhibitor, wrhile with chronic (repeated) administration it acts as an inducer.Drugs causing Enzyme InhibitionVitaminValproateKKetoconazoleCannotCimetidineCauseCiprofloxacinEnzymeErythromycinInhibitionDMH