This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pharmacology
Gentamycin is not given orally because: September 2005 
Select and explain. 
A. Adverse effects on gastric mucosa, B. Interferes with absorption of other drugs, C. Rapidly destroyed by gastric acid, D. Poor absorption
D: Poor absorption
Answer: D: Poor absorption 
Explanation: Ans. D: Poor absorption Like all aminoglycosides, when gentamicin is given orally, it is not systemically active. This is because it is not absorbed to any appreciable extent from the small intestine. It is administered intravenously, intramuscularly or topically to treat infections. Common propeies of aminoglycoside antibiotics Distribute extracellularly, do not penetrate brain/ CSF Act by interfering with bacterial protein synthesis. Completely eliminated unchanged in the urine by glomerular filtration. Narrow margin of safety. Bactericidal and more active at alkaline pH. Ototoxicity and nephrotoxic