Penicillin
Classification
I Penicillinase Sensitive
- Penicillin G (Benzyl penicillin), Procaine penicillin G, Benzathine penicillin G,
- Penicillin V (Phenoxymethyl penicillin).
- They are highly active against gram + ve cocci but are hydrolyzed by
- Penicillinase.
- Penicillin V is meant for oral use.
II Penicillinase Resistant
- Cloxacillin - It is resistant to degradation by Penicillinase.
- Mainly it exhibits activity against Gram + ve micro-organism and is useful against Penicillinase producing Staph Aureus.
III Broad Spectrum
Ampicillin; Ampicillin + Sulbactam sodium; Ampicillin + Probenecid; Ampicillin + Cloxacillin; Bacampicillin; Amoxycillin; Amoxycillin + Clavulanic Acid (Co-amoxiclav); Amoxycillin + Probenecid;
Have broad antibacterial spectrum and are effective against both gram +ve and gram -ve micro-organisms. These are hydrolyzed by Penicillinase.
VI Antipseudomonal Penicillins
Carbenicillins, Piperacillins, Azlocillins. These are indicated mainly to treat severe gram -ve bacterial infections. E.g. Pseudomonas, Enterobacter.
Mode of Action
The Penicillins are bactericidal and act by interfering with bacterial cell wall synthesis. After administration Penicillins are widely distributed throughout Body and therapeutic concentration is achieved in tissues and secretions such as pericardial fluid, pleural fluid, bile and joint fluid. Low concentrations of these drugs are found in brain tissue, prostatic secretions and intraocular fluid. Penicillins are excreted fast by the kidney, hence have short plasma half life. Blood levels of Penicillins are raised by administration of Probenecid. Oral penicillins are not used during acute stage of severe infections e.g. severe Pneumonia, bacteraemia, meningitis, empyema, pericarditis or septic arthritis.
S/P
Serious and sometimes fatal hypersensitivity (anaphylactoid) reactions may Occur. Extreme care should be exercised in patients with known allergies such as asthma, hay fever and urticaria since hypersensitivity reactions are more likely in these patients. Extreme caution in treating patient, with Infectious mononucleosis or lymphatic leukaemia since they are especially susceptible penicillin induced rashes. Prolonged therapy may result in the overgrowth of non-susceptible organisms. During prolonged therapy, periodic hepatic, renal function to be monitored. In treating urinary tract infections concomitant Probenecid therapy not required.
C/IM
Hypersensitivity to penicillins or cephalosporins.
Side Effects
Include skin rashes, pruritus, urticaria, serum sickness, fever, Herxheimer's reaction, anaphylactic reactions, nausea, diarrhoea, thrombocytopenia, leucopenia, eosinophilia, elevations in AST (SGOT) and ALT (SGPT) levels, irritation at the injection site, vein irritation and phlebitis following IV therapy and with high dose parenteral therapy, CNS toxicity including convulsions.