chapter
Antacids
Pages 2

Separate administration of agents that ↓ gastric acidity by 1-2 hours. However, absorption of itraconazole liquid solution does not require an acidic environment; it could be used instead and does not need to be given with food. Fluconazole absorption is not pH-dependent, so this is a suitable alternative

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DRUGS ACTING ON THE GASTROINTESTINAL TRACT ANTACIDS

↓ absorption Be aware

HEART FAILURE DRUGS – ACE INHIBITORS

fosinopril and enalapril

↓ absorption due to ≠ gastric pH Watch for poor response to ACE inhibitors

ANTACIDS ANTIMALARIALS – PROGUANIL, CHLOROQUINE

↓ chloroquine and proguanil levels ↓ absorption Separate doses by at least 4 hours

ANTACIDS ANTIPLATELET AGENTS – DIPYRIDAMOLE

Possible ↓ bioavailability of dipyridamole

Dipyridamole tablets require an acidic environment for adequate dissolution; ≠ pH of the stomach impairs dissolution and therefore may ↓ absorption of drug

≠ dose of dipyridamole or consider using an alternative antiplatelet drug

ANTACIDS ANTIPSYCHOTICS – PHENOTHIAZINES, SULPIRIDE

↓ levels of these antipsychotics ↓ absorption Separate doses by 2 hours (in the case of sulpiride, give sulpiride 2 hours after but not before the antacid)

ANTACIDS CONTAINING MAGNESIUM AND ALUMINIUM

BETA-BLOCKERS ≠ bioavailability of metoprolol and atenolol, which may produce a mild variation in response to both drugs

Variations in absorption of the respective beta-blockers

Clinical significance may be minimal but be aware. Monitor BP at least weekly until stable when initiating antacid therapy. Warn patients to report symptoms of hypotension (light-headedness, dizziness on standing, etc.)

ANTACIDS BISPHOSPHONATES ↓ bisphosphonate levels ↓ absorption Separate doses by at least 30 minutes ANTACIDS CONTAINING ALUMINIUM

DEFERASIROX ↓ levels of deferasirox ↓ absorption Avoid co-administration (manufacturers’ recommendation)