Comparative pharmacology of antibiotics

By Alex Yartsev - Dec 08, 2015

Both Question 3 from the second paper of 2006 and Question 9 from the second paper of 2003 asked the candidates to compare and contrast the pharmacology of ceftriaxone, gentamicin and meropenem. The answer to this specific question comes first in this chapter. It is not followed by a more indepth discussion of antibiotic pharmacology, because this would be something of a waste. it is unlikely that - after nine years of neglect - the college would bring this sort of question back into the papers.

A comparison of the selected antibiotics which the college was interested in:

	Ceftriaxone	Gentamicin	Meropenem
Class	3rd gen cephalosporin	Aminoglycoside	Carbapenem
Administration	IV – 1g; up to 3g/day	IV; daily dosing 5-7mg/kg	IV 1-2g – up to 6g/day
Pharmacokinetics	Cleared both renally (unchanged) and via biliary excretion (33%)	Cleared renally; rapidly and unchanged	Cleared renally
Mechanism of action	Inhibition of bacterial cell wall synthesis by binding to penicillin-binding proteins	Inhibition of bacterial protein synthesis by binding to the 30S subunit of the bacterial ribosome	Inhibition of bacterial cell wall synthesis by binding to penicillin-binding proteins
Indications	Infections by susceptible gram-positive organisms; Some gram-negative cover	Infections by susceptible gram-negative organisms; Little role in treatment of gram-positive infections (with the exception of enterococcal endocarditis)	Infection by susceptible gram-positive and gram negative aerobic and anaerobic organisms; broad cover
Precautions	Seizures in overdose Bone marrow suppression in chronic high-dose use Rapid development of microbial resistance	Nephrotoxicity Ototoxicity Accumulation in renal failure increases risk of toxicity Potentiates neuromuscular blockade	Seizures in overdose

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