Question

Review the drug-food and drug-drug interactions of the tetracyclines and the fluoroquinolones.

Answer 1

*Drug-Food interaction of Tetracyclines-

Specific food that is high in calcium such as dairy products(cheese,milk,yogurt or cottage cheese)can decrease the absorption of Tetracyclines from the stomach,Taking dairy products or other high calcium food together with Tetracyclines can decrease the effectiveness of Tetracyclines to treat the infection.To limit this interaction take Tetracyclines at least 1 hour before or 2 hours after meals or milk.

*Drug-Drug interaction of Tetracyclines-

1) Tetracyclines have chelating property-form insoluble and unabsorbable complexes with calcium and other metals.

So,milk,iron preparations,non systemic antacids and sucralfate reduce their absorption.

Administration of these substances and Tetracyclines should be staggered,if they cannot avoided altogether.

2) Enzyme inducers like Phenytoin and Phenobarbitone enhances metabolism and shortens the T1/2 of Tetracyclines.

*Drug-Food interaction of Fluoroquinolones-

Fluoroquinolones are rapidly absorbed orally,but food delays absorption and first pass metabolism occurs.

*Drug-Drug interaction of Fluoroquinolones-

1)plasma concentration of Theophylline, Caffeine and Warfarin is increased by Fluoroquinolones due to inhibition of metabolism

CNS toxicity can occur by concurrent use of Theophylline and Fluoroquinolones.

2)NSAIDs may enhance the CNS toxicity of Fluoroquinolones, seizures are reported.

3) Antacids, Sucralfate and Iron salts given concurrently reduce absorption of Fluoroquinolones.