Erythromycin and
clarithromycin increase the AUC of
sildenafil by 2- to 3-fold. It seems likely that
telithromycin will interact similarly. Erythromycin increases the AUC of
vardenafil 4-fold; it seems likely that
clarithromycin and
telithromycin will interact similarly.
Dosing guidance is given as follows:
Sildenafil for erectile dysfunction - consider a starting dose of 25 mg.
Sildenafil for
pulmonary hypertension - with
erythromycin 20 mg twice daily
erythromycin (UK advice. US states no dose reduction necessary). Recommended dose with
clarithromycin or
telithromycin 20 mg once daily. However, note that
erythromycin had a greater effect than
clarithromycin in the studies.
Vardenafil - the dose of
vardenafil should not exceed 5 mg in 24 hours with
erythromycin (UK and US). The dose of
vardenafil should not exceed 2.5 mg in 24 hours with
clarithromycin (US).