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
Antacid interfere with absorption of all of the following except: 
Select and explain. 
A. Ketoconazole, B. Azithromycin, C. Oxytetracycline, D. Ofloxacin
B: Azithromycin
Answer: B: Azithromycin 
Explanation: Ketoconazole dissolves at low pH: gastric acid is needed for its absorption.Therefore antacid interfere with its absorption.
Tetracyclines have chelating property- form insoluble and unabsorbable complexes with calcium and other metals. Milk, iron preparations, nonsystemic antacids and sucralfate reduce their absorption.  Administration of these substances and tetracyclines should be staggered, if they cannot be avoided altogether.
Azithromycin: The improved pharmacokinetic properties are acid-stability, rapid oral absorption (from empty stomach), larger tissue distribution and intracellular penetration.
Reference: Essentials of Medical Pharmacology Eighth Edition KD TRIPATHI page no 21,786,763,804