Potential for Pharmacodynamic Interactions with ADCIRCA
Do not use ADCIRCA in patients who are using any form of organic nitrate [see Contraindications ]. In clinical pharmacology studies ADCIRCA potentiated the hypotensive effect of nitrates [see Clinical Pharmacology]. In a patient who has taken ADCIRCA, where nitrate administration is deemed medically necessary in a lifeâ€“threatening situation, at least 48 hours should elapse after the last dose of ADCIRCA before nitrate administration is considered. In such circumstances, nitrates should still only be administered under close medical supervision with appropriate hemodynamic monitoring.
PDE5 inhibitors, including ADCIRCA, and alphaâ€“adrenergic blocking agents are both vasodilators with blood-pressure-lowering effects. When vasodilators are used in combination, an additive effect on blood pressure may be anticipated. Clinical pharmacology studies have been conducted with coadministration of tadalafil with doxazosin, alfuzosin or tamsulosin [see Warnings and Precautions and Clinical Pharmacology].
PDE5 inhibitors, including ADCIRCA, are mild systemic vasodilators. Clinical pharmacology studies were conducted to assess the effect of tadalafil on the potentiation of the bloodâ€“pressureâ€“lowering effects of selected antihypertensive medications (amlodipine, angiotensin II receptor blockers, bendroflumethiazide, enalapril, and metoprolol). Small reductions in blood pressure occurred following coadministration of tadalafil with these agents compared with placebo [see Warnings and Precautions and Clinical Pharmacology].
Both alcohol and tadalafil, a PDE5 inhibitor, act as mild vasodilators. When mild vasodilators are taken in combination, blood pressureâ€“lowering effects of each individual compound may be increased. Substantial consumption of alcohol (e.g., 5 units or greater) in combination with ADCIRCA can increase the potential for orthostatic signs and symptoms, including increase in heart rate, decrease in standing blood pressure, dizziness, and headache. Tadalafil (10 mg or 20 mg) did not affect alcohol plasma concentrations and alcohol did not affect tadalafil plasma concentrations. [See Warnings and Precautions and Clinical Pharmacology].
Potential for Other Drugs to Affect ADCIRCA
Ritonavir initially inhibits and later induces CYP3A, the enzyme involved in the metabolism of tadalafil. At steady state of ritonavir (about 1 week), the exposure to tadalafil is similar as in the absence of ritonavir [see Dosage and Administration Warnings and Precautions (5.2), and Clinical Pharmacology].
Other Potent Inhibitors of CYP3A
Tadalafil is metabolized predominantly by CYP3A in the liver. In patients taking potent inhibitors of CYP3A such as ketoconazole, and itraconazole, avoid use of ADCIRCA [see Warnings and Precautions and Clinical Pharmacology].
Potent Inducers of CYP3A
For patients chronically taking potent inducers of CYP3A, such as rifampin, avoid use of ADCIRCA [see Warnings and Precautions and Clinical Pharmacology].
Potential for ADCIRCA to Affect Other Drugs
Cytochrome P450 Substrates
Tadalafil is not expected to cause clinically significant inhibition or induction of the clearance of drugs metabolized by cytochrome P450 (CYP) isoforms (e.g., theophylline, warfarin, midazolam, lovastatin, bosentan) [see Clinical Pharmacology ].
Tadalafil (10 mg and 20 mg once daily) does not potentiate the increase in bleeding time caused by aspirin [see Clinical Pharmacology].
P-glycoprotein (e.g., digoxin)
Coadministration of tadalafil (40 mg once daily) for 10 days did not significantly alter digoxin pharmacokinetics in healthy subjects [see Clinical Pharmacology].