Use Additional Antacid With Didanosine Tablets?

Andrea Kovacs, MD

Disclosures

January 04, 2001

Question

Didanosine pediatric oral solution has to be mixed with an equal volume of antacid before administration. Can we do the same with didanosine dispersible tablets, in order to minimize gastric adverse effects?

Response from Andrea Kovacs, MD

Didanosine (dideoxyinosine, ddI) is an oral nucleoside reverse transcriptase inhibitor (NRTI) that is highly sensitive to degradation by acid pH (it is acid-labile). Absorption is variable among patients depending on the gastric pH, presence or absence of food, and formulation. Thus, when given orally it requires buffering to prevent degradation by stomach acids and to improve overall bioavailability. Present formulations available commercially contain buffering agents and in general it is recommended that ddI be given 1 hour before a meal. Chewable/dispersible, buffered tablets are buffered with magnesium hydroxide and calcium carbonate.

The official recommendation from the package insert[1] is to take ddI on an empty stomach 30 minutes before a meal. The chewable/dispersible, buffered tablets (or pediatric powder for oral formulation) should be thoroughly chewed, manually crushed, or dispersed in water before swallowing. It is recommended that 2 tablets be taken at the same time for maximal absorption and neutralization of gastric acid. For an infant aged less than 1 year, 1 tablet will achieve adequate neutralizing capacity, and this dosage may also decrease the chances of GI complaints. Tablets should not be swallowed whole. Tablets can be completely dispersed in 30 mL of water, and this can be further dispersed in apple juice if taste is a problem. This should be then swallowed immediately; it is stable for 1 hour. The package insert for chewable/dispersible ddI tablets states that the concomitant addition of magnesium- or aluminum-containing antacids may potentiate the adverse events associated with the antacid components; however, it is not contraindicated. The package insert does not state that antacids cannot be coadministered.

In addition, if your patient has heartburn or GI symptoms around the time that ddI is taken, an agent such as ranitidine could be taken. According to the package insert there is no significant pharmacokinetic interaction between ddI and ranitidine.

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