Drug Interaction Report

Itraconazole may increase plasma concentrations of bupivacaine. After itraconazole 200 mg/day orally for 4 days and single intravenous doses of bupivacaine 0.3 mg/kg were administered to healthy subjects, the plasma clearance of R- and S-bupivacaine was decreased by 20 to 25%. The mechanism is unknown, but may involve inhibition of CYP450 3A4 metabolism by itraconazole. The clinical significance is unknown, especially with regard to therapeutic doses of bupivacaine. Until more information is available, monitoring for cardiotoxicity and altered effects of bupivacaine is recommended if patients are concomitantly receiving itraconazole.

GENERALLY AVOID: Alcohol may potentiate the central nervous system (CNS) depressant effects of opioid analgesics including hydromorphone. Concomitant use may result in additive CNS depression and impairment of judgment, thinking, and psychomotor skills. In more severe cases, hypotension, respiratory depression, profound sedation, coma, or even death may occur.

GENERALLY AVOID: Consumption of alcohol while taking sustained-release formulations of hydromorphone may cause rapid release of the drug, resulting in high systemic levels of hydromorphone that may be potentially lethal even in opioid-tolerant patients. Alcohol appears to disrupt the extended release mechanism, causing 'dose-dumping' into the bloodstream. In 48 healthy volunteers, coadministration of a 12 mg dose of sustained-release hydromorphone with 240 mL of 40% (80 proof) alcohol resulted in a mean peak hydromorphone concentration (Cmax) approximately six times greater than when taken with water. One subject had a 16-fold increase in hydromorphone Cmax with 40% alcohol compared to water. In some subjects, coadministration with 8 ounces of 4% alcohol (equivalent to 2/3 of a typical serving of beer) resulted in almost twice the hydromorphone Cmax than when coadministered with water. The effect of alcohol was more pronounced in a fasted state.

MANAGEMENT: Patients taking sustained-release formulations of hydromorphone should not consume alcohol or use medications that contain alcohol on days of hydromorphone dosing. In general, potent narcotics such as hydromorphone should not be combined with alcohol.

ADJUST DOSING INTERVAL: Food increases the absorption of itraconazole capsules but decreases the absorption of itraconazole oral solution. Cola beverages may increase the bioavailability of itraconazole capsules. Itraconazole capsules require an acidic gastric pH for adequate dissolution and subsequent absorption. Cola beverages help lower gastric pH and improve absorption.

GENERALLY AVOID: Grapefruit juice may impair the absorption of itraconazole capsules, resulting in decreased antifungal effects. In a small, randomized, crossover study, the administration of itraconazole capsules with double-strength grapefruit juice (compared to water) was associated with significantly decreased (43%) plasma concentrations of itraconazole and its pharmacologically active hydroxy metabolite, as well as delayed times to reach peak concentrations of both. The exact mechanism of interaction is unknown but may involve reduced absorption of itraconazole secondary to enhanced activity of intestinal P-glycoprotein drug efflux pumps and delayed gastric emptying induced by certain compounds present in grapefruits. Another study reported no pharmacokinetic changes with single-strength grapefruit juice. Whether or not these observations apply to itraconazole oral solution is unknown.

MANAGEMENT: The manufacturer recommends that the capsules be taken immediately after a full meal and the solution be taken on an empty stomach to ensure maximal absorption. Cola beverages may help increase the bioavailability of itraconazole capsules, particularly in patients with hypochlorhydria or those treated concomitantly with gastric acid suppressants. Until more information is available, it may be advisable to avoid the consumption of grapefruits and grapefruit juice during itraconazole therapy.