Phenobarbital is the longest established anticonvulsant medication that is still used commonly to treat certain types of epilepsy. Following long-term treatment with phenobarbital, liver microsomal enzymes are ‘induced’ or up-regulated in terms of their activity. In view of this phenomenon, indicate what changes (increase, decrease or none) you would expect to occur in the following pharmacokinetic parameters for phenobarbital in an epileptic patient that has undergone six months of phenobarbital treatment compared to when they first started taking the drug. You should assume that microsomal enzyme induction has taken place in this person over the course of the six months. Please explain the reasoning behind your answers and provide literature support if available.
e) plasma half-life of other drugs metabolized by the same family of microsomal enzymes (10 pts)
Phenobarbitone is a barbiturate (malonyl urea ) Which is used in epilepsy.
It acts by increasing the lifetime of opening of chloride channel by acting on GABA - BZD receptor chloride channel.
Phenobarbitone induces several hepatic microsomal enzymes and increase the rate of their own metabolism as well as that of many other drugs.
ON REPEATED USE TOLERANCE AND DEPENDENCE OCCURS.
both cellular and pharmacokinetic tolerance developes on repeated use due to enzyme induction. Addicts may present with acute barbiturate intoxication. Psychological and physical dependence occurs and this drug has abuse liability.
Withdrawl symptoms are excitement, hallucinations, delirium, convulsions, etc.
Phenobarbotone induces glucuronyl transferase and reduce the effectiveness of other drugs. Such as warfarin, steriods , contraceptives, cholaramphenicol.
Additive action with other cns depressents . Such as alchol antihistaminics occurs..
Side effects are. Hangover , rashes, swelling of eyelids , tolerance and dependence ,.etc
Phenobarbital is the longest established anticonvulsant medication that is still used commonly to treat certain types of...
Phenobarbital is the longest established anticonvulsant medication that is still used commonly to treat certain types of epilepsy. Following long-term treatment with phenobarbital, liver microsomal enzymes are ‘induced’ or up-regulated in terms of their activity. In view of this phenomenon, indicate what changes (increase, decrease or none) you would expect to occur in the following pharmacokinetic parameters for phenobarbital in an epileptic patient that has undergone six months of phenobarbital treatment compared to when they first started taking the drug....