Drug Interactions between guanfacine and Hydromide

GENERALLY AVOID: Grapefruit juice may increase the plasma concentrations of guanfacine. The risk of adverse reactions such as hypotension, bradycardia, and sedation may increase. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruit. Ketoconazole, a potent CYP450 3A4 inhibitor, has been reported to increase guanfacine peak plasma concentration (Cmax) and systemic exposure (AUC) by approximately 2- and 3-fold, respectively. A computer simulation suggests that fluconazole, a moderate CYP450 3A4 inhibitor, would increase guanfacine Cmax and AUC by about 1.5- and 2-fold, respectively. In general, the effect of grapefruit juice is concentration-, dose- and preparation-dependent, and can vary widely among brands. Certain preparations of grapefruit juice (e.g., high dose, double strength) have sometimes demonstrated potent inhibition of CYP450 3A4, while other preparations (e.g., low dose, single strength) have typically demonstrated moderate inhibition.

GENERALLY AVOID: Alcohol may enhance the sedative and hypotensive effects of guanfacine.

GENERALLY AVOID: Administration of extended-release guanfacine with a high-fat meal may increase the bioavailability of guanfacine. When a single 4 mg dose of extended-release guanfacine was administered to adult volunteers with a high-fat breakfast, mean guanfacine peak plasma concentration (Cmax) and systemic exposure (AUC) increased by approximately 75% and 40%, respectively, compared to dosing in a fasted state.

MANAGEMENT: Patients treated with guanfacine should avoid consumption of grapefruit and grapefruit juice. In addition, it is preferable to avoid or limit the use of alcohol during treatment. Patients should be advised against driving or operating hazardous machinery until they know how the medication affects them. The extended-release formulation of guanfacine should not be taken together with a high-fat meal.

GENERALLY AVOID: Alcohol may potentiate the central nervous system (CNS) depressant effects of opioid analgesics including hydrocodone. 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 some sustained-release formulations of hydrocodone may cause rapid release of the drug, resulting in high systemic levels of hydrocodone that may be potentially lethal. Alcohol apparently can disrupt the release mechanism of some sustained-release formulations. In study subjects, the rate of absorption of hydrocodone from an extended-release formulation was found to be affected by coadministration with 40% alcohol in the fasted state, as demonstrated by an average 2.4-fold (up to 3.9-fold in one subject) increase in hydrocodone peak plasma concentration and a decrease in the time to peak concentration. Alcohol also increased the extent of absorption by an average of 1.2-fold (up to 1.7-fold in one subject).

GENERALLY AVOID: Grapefruit juice may increase the plasma concentrations of hydrocodone. The proposed mechanism is inhibition of CYP450 3A4-mediated metabolism of hydrocodone by certain compounds present in grapefruit. Increased hydrocodone concentrations could conceivably increase or prolong adverse drug effects and may cause potentially fatal respiratory depression.

MANAGEMENT: Patients taking sustained-release formulations of hydrocodone should not consume alcohol or use medications that contain alcohol. In general, potent narcotics such as hydrocodone should not be combined with alcohol. Patients should also avoid consumption of grapefruit or grapefruit juice during treatment with hydrocodone.