Age: In Phase 1, multiple-dose studies in which tolterodine immediate release 4 mg (2 mg bid) was administered, serum concentrations of tolterodine and of the 5-hydroxymethyl metabolite were similar in healthy elderly volunteers (aged 64 through 80 years) and healthy young volunteers (aged less than 40 years). In another Phase 1 study, elderly volunteers (aged 71 through 81 years) were given tolterodine immediate release 2 or 4 mg (1 or 2 mg bid). Mean serum concentrations of tolterodine and the 5-hydroxymethyl metabolite in these elderly volunteers were approximately 20% and 50% higher, respectively, than reported in young healthy volunteers. However, no overall differences were observed in safety between older and younger patients on tolterodine in Phase 3, 12-week, controlled clinical studies; therefore, no tolterodine dosage adjustment for elderly patients is recommended (see PRECAUTIONS, Geriatric Use).   
Pediatric: The pharmacokinetics of tolterodine have not been established in pediatric patients.   
Gender: The pharmacokinetics of tolterodine immediate release and the 5-hydroxymethyl metabolite are not influenced by gender. Mean C max of tolterodine (1.6 mcg/L in males versus 2.2 mcg/L in females) and the active 5-hydroxymethyl metabolite (2.2 mcg/L in males versus 2.5 mcg/L in females) are similar in males and females who were administered tolterodine immediate release 2 mg. Mean AUC values of tolterodine (6.7 mcg•h/L in males versus 7.8 mcg•h/L in females) and the 5-hydroxymethyl metabolite (10 mcg•h/L in males versus 11 mcg•h/L in females) are also similar. The elimination half-life of tolterodine for both males and females is 2.4 hours, and the half-life of the 5-hydroxymethyl metabolite is 3 hours in females and 3.3 hours in males.   
Race: Pharmacokinetic differences due to race have not been established.   
Renal Insufficiency: Renal impairment can significantly alter the disposition of tolterodine immediate release and its metabolites. In a study conducted in patients with creatinine clearance between 10 and 30 mL/min, tolterodine immediate release and the 5-hydroxymethyl metabolite levels were approximately 2 to 3 fold higher in patients with renal impairment than in healthy volunteers. Exposure levels of other metabolites of tolterodine (e.g., tolterodine acid, N-dealkylated tolterodine acid,  N-dealkylated tolterodine, and  N-dealkylated hydroxylated tolterodine) were significantly higher (10 to 30 fold) in renally impaired patients as compared to the healthy volunteers. The recommended dosage for patients with significantly reduced renal function is tolterodine tartrate tablets 1 mg twice daily (see PRECAUTIONS, General and DOSAGE AND ADMINISTRATION).   
Hepatic Insufficiency: Liver impairment can significantly alter the disposition of tolterodine immediate release. In a study conducted in cirrhotic patients, the elimination half-life of tolterodine immediate release was longer in cirrhotic patients (mean, 7.8 hours) than in healthy, young, and elderly volunteers (mean, 2 to 4 hours). The clearance of orally administered tolterodine was substantially lower in cirrhotic patients (1.0 ± 1.7 L/h/kg) than in the healthy volunteers (5.7 ± 3.8 L/h/kg). The recommended dose for patients with significantly reduced hepatic function is tolterodine tartrate tablets 1 mg twice daily (see PRECAUTIONS, General and DOSAGE AND ADMINISTRATION).