Omeprazole Dofetilide

Dofetilide is not administered with cimetidine because dofetilide plasma levels may be increased by as much as 50%. When treatment for gastric disorders is necessary, patients receiving dofetilide should take omeprazole ranitidine, or antacids as an alternative to cimetidine. 

Vincent J, Gardner MJ, Baris B, Willavize SA. Concurrent adm inistration of omeprazole and antacid does not alter the pharmacokinetics and phaim acody nam ic of dofetilide in healtiiy suh-iects. ClinPhamacolTher( 996) 59,182. 

An established interaction. Because of the likely increased risk of torsade de pointes, the manufacturer contraindicates the use of cimetidine in patients on dofetilide. This would seem to be a prudent precaution. This applies equally to cimetidine at over-the-counter doses, and patients on dofetilide should be warned to avoid this. No special precautions appear to be necessary with ranitidine. Note that omeprazole , (p.256) and antacids , (p.254) also appear not to interact with dofetilide. 

A study in 12 healthy subjects found that pretreatment with omeprazole 40 mg (10 or 2 hours before dofetilide) did not affect the pharmacokinetics of a single 500-microgram dose of dofetilide nor the dofetilide-induced change in QTc interval. No special precautions appear to be necessary. 

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