Erythromycin and
clarithromycin (and therefore probably telithromycin) are pre- dicted to raise
tadalafil levels by inhibiting its
metabolism by CYP3A4. This effect has been seen with other inhibitors of CYP3A4 (up to 4-fold rise with ketoconazole). Other
macrolides have less effect on CYP3A4, see
macrolides, and therefore seem less likely to interact.
The adverse effects of
tadalafil may be increased in some patients. The manufac- turers advise caution.