Tadalafil adverse effects

The most dramatic difference between the three agents is tadalahl s extended duration of action, earning it the nickname the weekender drug. While sildenafil and vardenafil have average half-lives of 3 to 4 hours, tadalafil s half life is approximately 18 hours.18 The extended half-life allows for more spontaneous sexual activity over a couple of days, but may increase the duration of adverse effects and liklihood of drug interactions or sildenafil. 

Unless otherwise stated, general information applies to the entire class of phosphodiesterase inhibitors. Sildenafil is highlighted because it was the first to be marketed and is the most thoroughly studied. The newer agents tadalafil and vardenafil have different pharmacokinetic profiles (Table 83-3), drug-food interactions, and adverse effects. 

Sildenafil and vardenafil decrease systolic/diastolic blood pressure by 8 to 10/5 to 6 mm Hg for 1 to 4 hours after a dose. Although most patients are asymptomatic, multiple antihypertensives, nitrates, and baseline hypotension increase the risk of developing adverse effects. Although tadalafil does not decrease blood pressure, it should be used with caution in patients with cardiovascular disease because of the inherent risk associated with sexual activity. 

Tadalafil has also been extensively evaluated in patients with cardiovascular disease and has a similar safety and efficacy profile to sildenafil (45). Studies have shown no adverse effects on cardiac contraction, ventricular repolarization, or ischemic threshold. A similar hypotensive effect has been recorded with a dose of doxazosin 8 mg so caution is needed. As hypotension does not occur in the supine position and as tadalafil has a long half-life it is suggested that tadalafil is taken in the morning and doxazosin in the evening. There is no interaction of tadalafil with the selective a-adrenoceptor antagonist tamsulosin, which can, therefore, be prescribed as an alternative to doxazosin for symptomatic benign prostate hypertrophy (46). 

Of particular interest is the daily use of tadalafil 10 mg which, after one week because of its half-life, is equivalent to 16-18 mg at steady state. In on-demand failures a regular dosing regime has been successful in 60% without increased adverse effects (47). This increases the chance of success with important implications for the more difficult cases and its use post radical prostatectomy as a daily regime is encouraging. There is no evidence of increased cardiovascular risk with on-demand, three times weekly, or daily dosing (48). 

PHOSPHODIESTERASE TYPE 5 INHIBITORS (e.g. sildenafil, tadalafil, vardenafil) GRAPEFRUIT JUICE Possibly t efficacy and t adverse effects, e.g. hypotension Small t in bioavailability, t variability in pharmacokinetics, i.e. interindividual variations in metabolism Safest to advise against intake of grapefruit juice for at least 48 hours prior to intending to take any of these preparations. When necessaiy, the starting dose of sildenafil should not exceed 25-50 mg and that of tadalafil 10 mg. Avoid co-administration with vardenafil... 

Visual adverse effects occur less frequently with vardenafll when compared with sildenafil (less than 0.1% versus 10%, respectively). Tadalafil has minimal to no inhibitory activity against type 6 phosphodiesterase, and no visual adverse effects have been reported. 

Priapism is a rare adverse effect of phosphodiesterase inhibitors, particularly sildenafil and vardenafil, which have shorter plasma half-lives than tadalafil. When priapism has occurred, this has been associated with excessive doses of the phosphodiesterase inhibitor or concomitant therapy involving other erectogenic drugs. 

In an open label, randomised study in 12 healthy subjects, ketoconazole 200 mg daily increased the AUC of a single 10-mg dose of tadalafil by twofold, and ketoconazole 400 mg daily increased the AUC fourfold. The manufacturers predict that itraconazole will interact similarly. This prediction has been borne out by a case report of a 56-year-old man who was taking itraconazole 400 mg daily for 7 days each month. Within a few hours of his first 10-mg dose of tadalafil he developed priapism, which lasted for more than 4 hours. The same reaction occurred when he took tadalafil during the following month. He had seemingly previously taken sildenafil with itraconazole without adverse effect. ... 

Sensory systems Adverse effects of PDE-5 inhibitors on the eyes have repeatedly been reported, but it is unclear whether these events are coincidental or related to drug-related effects on the ocular circulation or on other structures in the eye [27 ]. In a multicenter study 244 subjects were randomized to tadalafil 5 mg/day, sildenafil 50 mg/day, or placebo for 6 months [28. There was one case of retinal artery occlusion in a patient taking placebo and there were no abnormalities in electroretinogra-phy or visual function and no treatment-related findings suggestive of drug toxicity. 

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