Question

Describe, with the aid of diagrams, the mechanisms of action (65%), pharmacokinetics and side effects of β-lactam drugs, giving a drug example. (Pharmacology)

Answer 1

Answer : 1) Beta lactam group contains vast number of individual antibiotics having a common beta lactam ring in their structure . Penicillin is the most historically famous member of this group.Beta lactam antibiotics are bactericidal and act by binding with penicillin binding protein.This binding prevents synthesis of peptidoglycan, an essential component of bacterial cell wall. Absence of peptidoglycan make bacteria susceptible for lysis thus killing the bacteria .

2) Pharmacokinetics of penicillin - Different penicillins have different bioavailabilty. Penicillin G has bioavailabilty of less than 30 %. They have low protein binding capacity. Penicillin G has about 65%protein binding . Peak plasma time is 0.5 - 1 hour.They are mostly metabolised in liver and excreted in urine.

3) Adverse effects of penicillin -

*Diarrhoea

*Nausea and vomiting

*Hypersensitivity reaction ranging from mild to life threatening anaphylaxis

*Interstitial nephritis

* Jarisch Herxheimer reaction - Fever , shivering myalgia which may progress to shock, seen in syphilis patients treated with penicillin

* Can precipitate seizure

* Haemolytic anemia.