Metabolised primarily by CYP 2D6, and to some extent 3A4, but has not been found to inhibit or induce CYP 2C9 or 3A4 in therapeutic use.

Tolterodine is a synthetic tertiary amine antimuscarinic agent.

Tolterodine tartrate is used in the management of urinary frequency, urgency, and incontinence in detrusor instability, with actions similar to those of atropine. Given orally. Common adverse reactions of tolterodine that can be confused with an acute porphyric attack are vomiting, constipation, abdominal pain and dyspepsia.

Tolterodine is mainly metabolised in the liver by the cytochrome P450 isoenzyme CYP2D6 to the active 5-hydroxymethyl derivative, which is further metabolised to carboxylic acid an N-dealkylated 5- carboxylic acid. In poor metabolisers tolterodine is N-dealkylated by CYP 3A4. Listed by Rendic (2002) as a substrate for CYP 2C9, 2C19, 2D6, and 3A4, but not as an inhibitor or inducer. No evidence of Cyp-inductive properties. The manufacturer states that tolterodine does not appear to cause clinically important interactions with drugs metabolised by major microsomal cytochrome P-450 (CYP) isoenzymes.

Uneventful use reported in 2 patients with acute porphyria.