Royida Al Marastani
SEHA-Ambulatory Healthcare Services, UAE
Title: Drug interactions affecting drug bioavailability
Biography
Biography: Royida Al Marastani
Abstract
Drug-drug interactions (DDIs) are increased especially with polypharmacy patients leading to increased or decreased the clinical efficacy or increased the risk of the side effects or even the toxic effects.DDI can be classify into two classes pharmacokinetic and pharmacodynamic which affects the bioavailability of the drugs
Example 1:
H2 antagonists (e.g.ranitidine), antacids (e.g., aluminium hydroxide and sodium bicarbonate) and PPI (e.g., omeprazole, esomeprazole, pantoprazole) that increase the gastric pH lead to facilitate the absorption of beta-blockers .
Example 2:
Antifungal agents (e.g., ketoconazole or itraconazole), requires an acidic environment, therefore, their co-administration with drugs able to increase gastric pH, may cause a decrease in both dissolution and absorption of antifungal drugs. Therefore, antacid or anticholinergics, or PPI might be administered at least 2 h after the administration of antifungal agents.
Example 3:
The administration of drugs able to increase the gastric pH with ampicillin, atazanavir, clopidogrel, diazepam, methotrexate, vitamin B12, paroxetine and raltegravir are not recommended.
Example 4:
The administration of drugs that decrease the gastric pH (e.g., pentagastrin), may have an opposite effect.
Example 5:
Tetracyclines (e.g., doxycycline or minocycline) in the digestive tract can combine with metal ions (e.g., calcium, magnesium, aluminum, iron) to form complexes poorly absorbed. Consequently certain drugs (e.g., antacids, preparations containing magnesium salts, aluminum and calcium preparations containing iron) can significantly reduce the tetracyclines absorption.
Example 6:
Antacids reduce the absorption of fluoroquinolones (e.g., ciprofloxacin), penicillamines and tetracyclines, because the metal ions form complexes with the drug. So antacids and fluoroquinolones should be administered at least 2 h apart or more.
Example 7:
Metoclopramide, may accelerate gastric emptying, hence decreasing the absorption of digoxin and theophylline whereas it can accelerate the absorption of alcohol, acetylsalicylic acid, acetaminophen, tetracycline and levo-dopa.