Drug Interaction Report

MONITOR: Coadministration with inhibitors of CYP450 3A4 and/or 2D6 may increase the plasma concentrations of tamsulosin, which is primarily metabolized in the liver by these isoenzymes. In 24 healthy volunteers, administration of a single 0.4 mg dose of tamsulosin with the potent CYP450 3A4 inhibitor ketoconazole (400 mg once daily for 5 days) resulted in a 2.2-fold increase in tamsulosin peak plasma concentration (Cmax) and a 2.8-fold increase in systemic exposure (AUC) compared to administration alone. Likewise, concomitant treatment with the potent CYP450 2D6 inhibitor paroxetine (20 mg once daily for 9 days) resulted in an increase in the Cmax and AUC of a single 0.4 mg dose of tamsulosin by a factor of 1.3 and 1.6, respectively. The effects of concomitant administration of a moderate CYP450 3A4 inhibitor such as erythromycin or a moderate CYP450 2D6 inhibitor such as terbinafine on the pharmacokinetics of tamsulosin have not been evaluated. The effects of coadministration of both a CYP450 3A4 and a CYP450 2D6 inhibitor have also not been evaluated. However, there is a potential for significant increase in tamsulosin exposure relative to coadministration with either inhibitor alone. Similarly, a significant increase in exposure may occur when tamsulosin is administered with a CYP450 3A4 inhibitor to individuals who have genetic polymorphisms of CYP450 2D6 resulting in reduced or absent enzyme activity, or so-called CYP450 2D6 poor metabolizers (approximately 7% of Caucasians and less than 2% of Asians and individuals of African descent).

MANAGEMENT: Caution is advised if tamsulosin is used concomitantly with moderate CYP450 3A4 inhibitors (e.g., amiodarone, aprepitant, diltiazem, dronedarone, erythromycin, fluconazole, fluvoxamine, fusidic acid, imatinib, isavuconazonium, verapamil) and/or moderate to potent CYP450 2D6 inhibitors (e.g., abiraterone, bupropion, celecoxib, cinacalcet, darifenacin, dronedarone, duloxetine, fluoxetine, lorcaserin, paroxetine, propafenone, quinidine, ranolazine, rolapitant, terbinafine), particularly at a dosage higher than 0.4 mg/day. The potential for increased risk of adverse effects such as postural hypotension, syncope, and priapism should be considered. It should be noted that rolapitant, a moderate CYP450 2D6 inhibitor, can increase plasma concentrations and the risk of adverse effects of tamsulosin for at least 28 days after administration of rolapitant. Patients should be advised to avoid rising abruptly from a sitting or recumbent position, and to notify their physician if they experience dizziness, lightheadedness, syncope, orthostasis, or tachycardia. Patients should also avoid driving or operating hazardous machinery until they know how the medication affects them.

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MONITOR: Ranolazine can cause dose-related prolongation of the QT interval. Theoretically, coadministration with other agents that can prolong the QT interval may result in additive effects and increased risk of ventricular arrhythmias including torsade de pointes and sudden death, although there is little experience in this setting. At Tmax following repeat dosing of 1000 mg twice daily, the mean effect of ranolazine on QTc is approximately 6 msec. However, in 5% of the population with the highest plasma concentrations, the prolongation of QTc is 15 msec or more. The relationship between ranolazine plasma level and QTc remains linear over a concentration range up to 4-fold greater than the concentrations produced by a dosage of 1000 mg twice a day, and this relationship is not significantly affected by age, weight, gender, race, heart rate, congestive heart failure, diabetes, or renal impairment. However, the apparent linear relationship is much steeper in cirrhotic subjects with mild or moderate hepatic impairment. Ranolazine did not induce torsade de pointes or other arrhythmias in several in vitro and animal models. There have also been no reported cases of torsade de pointes in clinical studies of ranolazine comprising 3,669 patient-years of treatment. In fact, ranolazine was found to be antiarrhythmic in Study CVT 3036 (MERLIN-TIMI 36), which was a Phase 3, randomized, double-blind, parallel-group, placebo-controlled clinical trial designed to evaluate the efficacy and safety of ranolazine as chronic therapy in patients with non-ST elevation acute coronary syndromes (ACS) treated with other standard therapy. No proarrhythmic effects were observed on 7-day Holter recordings in 3,162 ACS patients treated with ranolazine. There was a significantly lower incidence of arrhythmias (ventricular tachycardia, bradycardia, supraventricular tachycardia, and new atrial fibrillation) in patients treated with ranolazine (80%) versus placebo (87%), including ventricular tachycardia >= 3 beats (52% versus 61%). In general, the risk of an individual agent or a combination of agents causing ventricular arrhythmia in association with QT prolongation is largely unpredictable but may be increased by certain underlying risk factors such as congenital long QT syndrome, cardiac disease, and electrolyte disturbances (e.g., hypokalemia, hypomagnesemia). In addition, the extent of drug-induced QT prolongation is dependent on the particular drug(s) involved and dosage(s) of the drug(s).

MANAGEMENT: Caution is recommended if ranolazine is used in combination with other drugs that can prolong the QT interval. Since the magnitude of QTc prolongation increases with increasing plasma concentrations of ranolazine, the maximum recommended dosage of 1000 mg twice daily should not be exceeded. Patients should be advised to seek prompt medical attention if they experience symptoms that could indicate the occurrence of torsade de pointes such as dizziness, lightheadedness, fainting, palpitation, irregular heart rhythm, shortness of breath, or syncope. Ranolazine is contraindicated in patients with liver cirrhosis because of the profound effect on QT prolongation in this population.

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MONITOR: Coadministration with inhibitors of CYP450 3A4 and/or 2D6 may increase the plasma concentrations of tamsulosin, which is primarily metabolized in the liver by these isoenzymes. In 24 healthy volunteers, administration of a single 0.4 mg dose of tamsulosin with the potent CYP450 3A4 inhibitor ketoconazole (400 mg once daily for 5 days) resulted in a 2.2-fold increase in tamsulosin peak plasma concentration (Cmax) and a 2.8-fold increase in systemic exposure (AUC) compared to administration alone. Likewise, concomitant treatment with the potent CYP450 2D6 inhibitor paroxetine (20 mg once daily for 9 days) resulted in an increase in the Cmax and AUC of a single 0.4 mg dose of tamsulosin by a factor of 1.3 and 1.6, respectively. The effects of concomitant administration of a moderate CYP450 3A4 inhibitor such as erythromycin or a moderate CYP450 2D6 inhibitor such as terbinafine on the pharmacokinetics of tamsulosin have not been evaluated. The effects of coadministration of both a CYP450 3A4 and a CYP450 2D6 inhibitor have also not been evaluated. However, there is a potential for significant increase in tamsulosin exposure relative to coadministration with either inhibitor alone. Similarly, a significant increase in exposure may occur when tamsulosin is administered with a CYP450 3A4 inhibitor to individuals who have genetic polymorphisms of CYP450 2D6 resulting in reduced or absent enzyme activity, or so-called CYP450 2D6 poor metabolizers (approximately 7% of Caucasians and less than 2% of Asians and individuals of African descent).

MANAGEMENT: Caution is advised if tamsulosin is used concomitantly with moderate CYP450 3A4 inhibitors (e.g., amiodarone, aprepitant, diltiazem, dronedarone, erythromycin, fluconazole, fluvoxamine, fusidic acid, imatinib, isavuconazonium, verapamil) and/or moderate to potent CYP450 2D6 inhibitors (e.g., abiraterone, bupropion, celecoxib, cinacalcet, darifenacin, dronedarone, duloxetine, fluoxetine, lorcaserin, paroxetine, propafenone, quinidine, ranolazine, rolapitant, terbinafine), particularly at a dosage higher than 0.4 mg/day. The potential for increased risk of adverse effects such as postural hypotension, syncope, and priapism should be considered. It should be noted that rolapitant, a moderate CYP450 2D6 inhibitor, can increase plasma concentrations and the risk of adverse effects of tamsulosin for at least 28 days after administration of rolapitant. Patients should be advised to avoid rising abruptly from a sitting or recumbent position, and to notify their physician if they experience dizziness, lightheadedness, syncope, orthostasis, or tachycardia. Patients should also avoid driving or operating hazardous machinery until they know how the medication affects them.

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GENERALLY AVOID: Grapefruit and grapefruit juice may significantly increase the plasma concentrations of orally administered ranolazine. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruit. Because ranolazine prolongs QT interval in a dose-dependent manner, high plasma levels of ranolazine may increase the risk of ventricular arrhythmias such as ventricular tachycardia, ventricular fibrillation, and torsade de pointes.

MANAGEMENT: Patients treated with ranolazine should avoid consumption of grapefruit juice and other grapefruit products if possible. Otherwise, the dosage of ranolazine should be limited to 500 mg twice a day.

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GENERALLY AVOID: Alcohol may potentiate some of the pharmacologic effects of sertraline. Use in combination may result in additive central nervous system depression and/or impairment of judgment, thinking, and psychomotor skills. In addition, limited clinical data suggest that consumption of grapefruit juice during treatment with sertraline may result in increased plasma concentrations of sertraline. The proposed mechanism is inhibition of CYP450 3A4-mediated metabolism by certain compounds present in grapefruit. An in-vitro study demonstrated that grapefruit juice dose-dependently inhibits the conversion of sertraline to its metabolite, desmethylsertraline. In a study with eight Japanese subjects, mean plasma levels of sertraline increased by approximately 100% and maximum plasma concentrations increased by 66% after the ingestion of three 250 mL glasses of grapefruit juice per day for 5 days and administration of a single dose of sertraline 75 mg on the sixth day. In another small study with 5 patients, mean sertraline trough levels increased by 47% after taking sertraline for at least 6 weeks, then taking sertraline with 240 mL grapefruit juice daily for 1 week. The clinical significance is unknown; however, pharmacokinetic alterations associated with interactions involving grapefruit juice are often subject to a high degree of interpatient variability. The possibility of significant interaction in some patients should be considered.

MANAGEMENT: Patients receiving sertraline should be advised to avoid or limit consumption of alcohol. Ambulatory patients should be counseled to avoid hazardous activities requiring complete mental alertness and motor coordination until they know how sertraline affects them, and to notify their physician if they experience excessive or prolonged CNS effects that interfere with their normal activities. Some authorities recommend that consumption of grapefruit juice should be avoided during sertraline therapy.

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GENERALLY AVOID: Moderate-to-high dietary intake of potassium, especially salt substitutes, may increase the risk of hyperkalemia in some patients who are using angiotensin II receptor blockers (ARBs). ARBs can promote hyperkalemia through inhibition of angiotensin II-induced aldosterone secretion. Patients with diabetes, heart failure, dehydration, or renal insufficiency have a greater risk of developing hyperkalemia.

MANAGEMENT: Patients should receive dietary counseling and be advised to not use potassium-containing salt substitutes or over-the-counter potassium supplements without consulting their physician. If salt substitutes are used concurrently, regular monitoring of serum potassium levels is recommended. Patients should also be advised to seek medical attention if they experience symptoms of hyperkalemia such as weakness, irregular heartbeat, confusion, tingling of the extremities, or feelings of heaviness in the legs.

MONITOR: Grapefruit juice may modestly decrease and delay the conversion of losartan to its active metabolite, E3174. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruits. The clinical significance is unknown. Moreover, pharmacokinetic alterations associated with interactions involving grapefruit juice are often subject to a high degree of interpatient variability.

MANAGEMENT: Patients who regularly consume grapefruits and grapefruit juice should be monitored for altered efficacy of losartan. Grapefruits and grapefruit juice should be avoided if an interaction is suspected. Orange juice is not expected to interact.

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ADJUST DOSING INTERVAL: Food may delay the gastrointestinal absorption of tamsulosin. The time to maximum plasma concentration (Tmax) is reached by 4 to 5 hours under fasted conditions and by 6 to 7 hours when tamsulosin is administered with food. The delay in Tmax has the desirable effect of smoothing the tamsulosin plasma concentration profile, thereby reducing fluctuation of the plasma peak and trough concentrations with multiple dosing. Food may also affect the extent of absorption of tamsulosin. It has been reported that taking tamsulosin under fasted conditions results in a 30% increase in bioavailability (AUC) and 40% to 70% increase in peak plasma concentration (Cmax) compared to fed conditions. The effects of food on the pharmacokinetics of tamsulosin are consistent regardless of whether tamsulosin is taken with a light meal or a high-fat meal.

MANAGEMENT: To ensure uniformity of absorption, tamsulosin should be administered approximately one-half hour following the same meal each day.

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