General Principles of Antimicrobial Therapy MCQs

Clarithromycin can be administered less frequently than erythromycin, but it is not effective in single doses against susceptible organisms. Organisms resistant to erythromycin, including pneumococci and methicillin-resistant staphylococci, are also resistant to other macrolides. Drug interactions have occurred with clarithromycin, through its ability to inhibit cytochrome P450. Clarithromycin is more active than erythromycin against Maxium complex, Tgondii, and H pylori.

This patient with CXR of lung abscess, treated with Clindamycin. It is a bacteriostatic antibiotic that inhibits bacterial protein synthesis by preventing peptide translocation at the 50S (large) ribosomal subunit. It targets anaerobic organisms and is commonly used for the treatment of aspiration pneumonia and lung abscess, which are typically polymicrobial. Clostridioides difficile colitis is a potential complication of clindamycin. Reference: Basic & Clinical Pharmacology, Fourteenth Edition By Bertram G. Katzung Pg. no. 836

As per given clinical scenario, patient with an incomplete immunisation record, signs of an upper respiratory infection (nasal discharge, low-grade fever) and intense paroxysmal coughing with a high-pitched "Whooping" sound indicate pertussis (whooping cough). Azithromycin is the treatment of choice. Early administration of macrolides can lessen symptoms in the catarrhal and paroxysmal stage. Therefore, oral azithromycin is indicated in this patient. Reference: Basic & Clinical Pharmacology, Fourteenth Edition By Bertram G. Katzung Pg. no. 820

Clindamycin is a bacteriostatic antibiotic that inhibits bacterial protein synthesis by preventing peptide translocation at the 50S (large) ribosomal subunit. It targets anaerobic organisms and is commonly used for the treatment of aspiration pneumonia and lung abscess, which are typically polymicrobial. Clostridioides difficile colitis is a potential complication of clindamycin. Reference: Basic & Clinical Pharmacology, Fourteenth Edition By Bertram G. Katzung Pg. no. 837

Therapeutic drug monitoring (TDM) is particularly useful in the following situations: Drugs with low safety margin, e.g. digoxin, anticonvulsants, antiarrhythmics, theophylline, aminoglycoside antibiotics, lithium, tricyclic antidepressants. If individual variations are large, e.g. antidepressants, lithium. Potentially toxic drugs used in the presence of renal failure, e.g. aminoglycoside antibiotics, vancomycin. In case of poisoning. In case of failure of response without any apparent reason, e.g. antimicrobials. To check patient compliance, e.g. psychopharmacological agents.

Synergy is a term used to describe a situation when the combined effect of two or more drugs simultaneously is greater than can be explained by arithmetically adding the individual effects. A fine example is the synergistic effect when penicillin such as ampicillin is combined with an amino-glycoside such as gentamicin. An agonist is a molecule that elicits a response from a receptor by binding to it. The term can refer to endogenous or exogenous compounds. Anergy refers to a lack of the body’s immune system to mount a normal response to an antigen. It does not describe cooperation between drugs. Symbiosis refers to a mutually beneficial relationship between organisms. It is not used to describe interactions between medications. Reference: Basic & Clinical Pharmacology by Bertram G. Katzung Fourteenth Edition Pg no. 22

Initial regimen for mycobacterium avium: At least two-antimycobacterial drugs; preferred agents include: Macrolide: clarithromycin (first-line) OR azithromycin AND ethambutol Reference: Harrison's principles of internal medicine - 20 th addition Page no. 1278