Solifenacin is extensively metabolized by Cyp3A4, but it has no capacity for Cyp-induction or significant Cyp-inhibition.

Dihydroisoquinoline tertiary amine.

Solifenacin is an anticholinergic spasmolytic used in the treatment of overactive bladder with symptoms of urge urinary incontinence, urgency, and increased urinary frequency. It is administered orally. Common adverse reactions of solifenacin that can be confused with an acute porphyric attack are constipation, nausea and abdominal pain. Side effects such as nausea may be potentially porphyrinogenic through reduction in caloric intake. Urinary infection is an uncommon side effect but may also potentially be porphyrinogenic.

Solifenacin is eliminated mainly via hepatic metabolism by Cyp3A4, and only 3-13 % is excreted as unchanged drug in urine. The absolute bioavailability is about 90%. Solifenacin has a high fraction of plasma protein-binding (93-96%). Solifenacin doses not influence the activities of Cyps 1A1, 1A2, 2C9, 2D6 and 3A4, but shows weak and clinically insignificant inhibitory potential for Cyp 2C19 and p-glycoprotein.(Doroshyenko 2009). In a well-controlled therapeutic trial solifenacin did not interact with the metabolism of ethinyl estradiol or levonorgestrel administered in oral contraception. (Taekema-Roelvink 2005).

Uneventful use reported in 2 patients with acute porphyria.