Detrol
Tolterodine--a new bladder-selective antimuscarinic agent.

Nilvebrant L, Andersson KE, Gillberg PG, Stahl M, Sparf B.

Medical Department Urology, Pharmacia & Upjohn AB, Uppsala, Sweden.

Tolterodine is a new muscarinic receptor antagonist intended for the treatment of urinary urge incontinence and other symptoms related to an overactive bladder. The aim of the present study was to compare the antimuscarinic properties of tolterodine with those of oxybutynin, in vitro and in vivo. Tolterodine effectively inhibited carbachol-induced contractions of isolated strips of urinary bladder from guinea pigs (K(B) 3.0 nM; pA2 8.6; Schild slope 0.97) and humans (K(B) 4.0 nM; pA2 8.4; Schild slope 1.04) in a concentration-dependent, competitive manner. The affinity of tolterodine was similar to that derived for oxybutynin (K(B) 4.4 nM; pA2 8.5; Schild slope 0.89) in the guinea-pig bladder. Tolterodine (21-2103 nmol/kg (0.01-1 mg/kg); intravenous infusion) was significantly more potent in inhibiting acetylcholine-induced urinary bladder contraction than electrically-induced salivation in the anaesthetised cat. In contrast, oxybutynin displayed the opposite tissue selectivity. Radioligand binding data showed that tolterodine bound with high affinity to muscarinic receptors in urinary bladder (K(i) 2.7 nM), heart (K(i) 1.6 nM), cerebral cortex (K(i) 0.75 nM) and parotid gland (K(i) 4.8 nM) from guinea pigs and in urinary bladder from humans (K(i) 3.3 nM). Tolterodine and oxybutynin were equipotent, except in the parotid gland, where oxybutynin bound with 8-times higher affinity (K(i) 0.62 nM). Binding data on human muscarinic m1-m5 receptors expressed in Chinese hamster ovary cells showed that oxybutynin, in contrast to tolterodine, exhibits selectivity (10-fold) for muscarinic m3 over m2 receptors. The K(B) value determined for oxybutynin (4.4 nM) in functional studies on guinea-pig bladder correlated better with the binding affinity at muscarinic M2/m2 receptors (K(i) 2.8 and 6.7 nM) than at muscarinic M3/m3 receptors (K(i) 0.62 and 0.67 nM). The tissue selectivity demonstrated for tolterodine in vivo cannot be attributed to selectivity for a single muscarinic receptor subtype. However, the combined in vitro and in vivo data on tolterodine and oxybutynin may indicate either that muscarinic M3/m3 receptors in glands are more sensitive to blockade than those in bladder smooth muscle, or that muscarinic M2/m2 receptors contribute to bladder contraction.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9200560&dopt=Abstract tolterodine Detrol



Detrol
Antimuscarinic potency and bladder selectivity of PNU-200577, a major metabolite of tolterodine.

Nilvebrant L, Gillberg PG, Sparf B.

Medical Department Urology, Pharmacia & Upjohn AB, Uppsala, Sweden.

PNU-200577 (labcode DD 01 [(R)-N, N-diisopropyl-3-(2-hydroxy-5-hydroxymethylphenyl)-3-phenylpropanamine ) is a major pharmacologically active metabolite of tolterodine, a new muscarinic receptor antagonist intended for the treatment of an overactive bladder. In vitro, PNU-200577 produced a competitive and concentration-dependent inhibition of carbachol-induced contraction of guinea-pig isolated urinary bladder strips (KB = 0.84 nM; pA2 = 9.14). In vivo, PNU-200577 was significantly more potent at inhibiting acetylcholine-induced urinary bladder contraction than electrically induced salivation in the anaesthetised cat (ID50 15 and 40 nmol.kg-1, respectively; P < 0.01). In radioligand binding studies carried out in homogenates of guinea-pig tissues and Chinese hamster ovary cell lines expressing human muscarinic m1-m5 receptors, PNU-200577 was not selective for any muscarinic receptor subtype. Thus, PNU-200577 is similar to tolterodine in terms of antimuscarinic potency, functional selectivity for the urinary bladder in vivo and absence of selectivity for muscarinic receptor subtypes in vitro. The results of this study clearly indicate that PNU-200577 contributes to the therapeutic action of tolterodine, in view of its high antimuscarinic potency, similar serum concentration and lower degree of protein binding.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9353847&dopt=Abstract tolterodine Detrol



Detrol
Determination of tolterodine and the 5-hydroxymethyl metabolite in plasma, serum and urine using gas chromatography-mass spectrometry.

Palmer L, Andersson L, Andersson T, Stenberg U.

Department of Bioanalytical Chemistry, Pharmacia & Upjohn AB, Uppsala, Sweden.

A specific and sensitive capillary gas chromatography-mass spectrometry assay for the determination of tolterodine and the 5-hydroxymethyl metabolite (Labcode DD 01) in plasma, serum and urine is described. Extraction of the analytes was performed with liquid/liquid or solid-phase extraction prior to derivatisation with a silyl reagent. The derivatives were quantified by selected ion monitoring mass spectrometry using deuterium-labelled internal standards. A single level calibration curve was utilised for quantification of plasma, serum and urine concentrations of tolterodine and DD 01. The accuracy (inter- and intra-day) for both analytes was within 87-110% in the range 0.5 and 50 ng ml-1 and precision was better than 90%. Overall, this method was shown to be reliable for pharmacokinetic assays of tolterodine and the metabolite DD 01 in samples from preclinical and clinical studies.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9447563&dopt=Abstract tolterodine Detrol



Detrol
Tolterodine, a new muscarinic receptor antagonist, is metabolized by cytochromes P450 2D6 and 3A in human liver microsomes.

Postlind H, DanielsonA, Lindgren A, Andersson SH.

Department of Drug Metabolism, Pharmacia & Upjohn AB, Uppsala, Sweden.

Tolterodine, a new muscarinic receptor antagonist, is metabolized via two pathways: oxidation of the 5-methyl group and dealkylation of the nitrogen. In an attempt to identify the specific cytochrome P450 enzymes involved in the metabolic pathway, tolterodine was incubated with microsomes from 10 different human liver samples where various cytochrome P450 activities had been rank ordered. Strong correlation was found between the formation of the 5-hydroxymethyl metabolite of tolterodine (5-HM) and CYP2D6 activity (r2, 0.87), as well as between the formation of N-dealkylated tolterodine and CYP3A activity (r2, 0.97). When tolterodine was incubated with human liver microsomes in the presence of compounds known to interact with different P450 isoforms, quinidine was found to be the strongest inhibitor of the formation of 5-HM. Ketoconazole and troleandomycin were found to be the strongest inhibitors of the formation of N-dealkylated tolterodine. A weak inhibitory effect on the formation of N-dealkylated tolterodine was found with sulfaphenazole, whereas tranylcypromine did not inhibit the formation of this metabolite. Microsomes from cells overexpressing CYP2D6 formed 5-HM, whereas N-dealkylated tolterodine was formed by microsomes expressing CYP2C9, -2C19, and -3A4. The Km for formation of N-dealkylated tolterodine by CYP3A4 was similar to that obtained in human liver microsomes and higher for CYP2C9 and -2C19. We conclude from these studies that the formation of 5-HM is catalyzed by CYP2D6 and that the formation of N-dealkylated tolterodine is predominantly catalyzed by CYP3A isoenzymes in human liver microsomes.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9531513&dopt=Abstract tolterodine Detrol