Tadalafil drug interactions

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Authored by: Wqli 12:24, 28 March 2007 (PDT)
Certified by: Rlweber 14:54, 24 April 2007 (PDT)

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Drug-drug interactions

Severity levelClick here to see Severity Level Legend Drug and description of interaction
4 organic nitrates: Consistent with its known effects on the nitric oxide/cGMP pathway, tadalafil was shown to potentiate the hypotensive effects of nitrates and therefore its use in patients who are using any form of organic nitrates (either regularly and/or intermittently) is contraindicated.[1][2]
3 alpha1-blockers: PDE5 inhibitors may enhance the hypotensive effect of alpha1-blockers. The adverse clinical effects observed during concomitant administration are likely due to additive vasodilatory effects. Co-administration of an alpha1-blocker (chronic and/or stable) with a single dose of a PDE5 inhibitor results in mild reductions in blood pressure with generally mild symptoms; dizziness and lightheadedness.[1] However, symptomatic hypotension (systolic BP <85 mmHg) has been reported. This interaction appears more likely with doxazosin and terazosin than with tamsulosin.[3]

CYP 3A4 inhibitors, imidazoles (antifungal agents), macrolide antibiotics, protease inhibitors: May decrease the metabolism of PDE5 inhibitors via CYP isoenzymes resulting in an increase in PDE5-induced adverse effects, such as hypotension, dyspepsia, headache, visual changes, and priapism. If co-administered, monitor for adverse events.[1][4]

2 CYP 3A4 inducers: May increase the metabolism of tadalafil, leading to decreased efficacy.[1]
1 None known

Drug-food/drug-herb interactions

Severity levelClick here to see Severity Level Legend Drug and description of interaction
4 None known
3 None known
2 grapefruit juice: May inhibit the metabolism of CYP3A4 substrates, resulting in an increase in PDE5-induced adverse effects.[1]

ethanol: Both alcohol and PDE5 inhibitors, act as mild vasodilators. When used in combination, blood pressure lowering effects of each individual compound may be increased. Substantial consumption of alcohol (5 units or greater) in combination with tadalafil can increase the potential for orthostatic signs and symptoms; increase heart rate, decrease in standing blood pressure, dizziness, and headache.[1]

1 None known

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 Cialis® (Tadalafil) Package Insert. Indianapolis, IN; Eli Lilly and Company; 2007 Jan.
  2. ↑ Kloner RA. Hutter AM. Emmick JT. Mitchell MI. Denne J. Jackson G. Time course of the interaction between tadalafil and nitrates. Journal of the American College of Cardiology. 42(10):1855-60, 2003 Nov 19.
  3. ↑ Auerbach SM. Gittelman M. Mazzu A. Cihon F. Sundaresan P. White WB. Simultaneous administration of vardenafil and tamsulosin does not induce clinically significant hypotension in patients with benign prostatic hyperplasia. Urology. 64(5):998-1003; discussion 1003-4, 2004 Nov.
  4. ↑ Galatti L. Fioravanti A. Salvo F. Polimeni G. Giustini SE. Interaction between tadalafil and itraconazole. Annals of Pharmacotherapy. 39(1):200, 2005 Jan.
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