Bioavailability of Vagantin® Coated Tablets Relative to an Oral Methantheline Bromide Solution

The quarternary anticholinergic compound methantheline bromide (diethyl-methyl [2-(9 xanthenyl carbonyloxy) ethyl] ammonium bromide) is marketed to treat neurogenic bladder instability. In comparison with atropine, it influences the parasympathetic nervous transmission more by ganglionic rather than peripheral muscarinic receptor blockade. Clinical effects after single therapeutic doses of 50-100 mg last for about 6 hours which is longer than after atropine. The drug relaxes smooth muscles of the gastrointestinal and urogenital tract. Furthermore, it inhibits bronchial, salivary and sweat glands secretion, lowers the production of gastric juice and disturbs accommodation.

There are no data available on the pharmacokinetic properties of methantheline in man. However, 25-50 mg intravenous methantheline seem to be equivalent to 50-100 mg p.o. with regard to the pharmacodynamic effects [Stille 1988].

Vagantin® is marketed as coated tablets containing 50 mg methantheline bromide. Because of the particular properties of methantheline (narrow therapeutic range, obviously erratic, incomplete and irregular absorption) and because of the national and international recommendations concerning the registration of drugs, Vagantin® must be evaluated with regard to its pharmacokinetic properties at least relative to a non-formulated form.

Inclusion criteria

• age: 18 - 45 years
• sex: male and female
• ethnic origin: Caucasian
• body weight: ±20 % of normal weight (Broca)
• good health as evidenced by the results of the clinical examination and the laboratory check-up which are judged by the clinical investigator not to differ in a clinical relevant way from the normal state
• written informed consent

Exclusion criteria

• known hypersensitivity to the investigational products or to their adjuvants
• pollakisurie of cardial and renal reasons
• megacolon
• atonia of the gastrointestinal tract
• atonia or hypotonia of the urinary bladder
• tachycardiac arrhythmia
• subvesical bladder obstruction, especially benign prostatic hypertrophy
• narrow angle glaucoma
• glasses or contact lenses
• history of gastrointestinal diseases (except appendectomy)
• history of renal and/or hepatic diseases
• any disease known to modify absorption, metabolism or excretion of the drug under investigation
• liability to orthostatic dysregulation, faintings, or blackouts
• alcohol consumption more than 40 g/day
• smokers of more than 10 cigarettes per day
• special or uniform nutritional habits, e.g. vegetarians or under-caloric diet
• less than 14 days after last acute disease
• less than 14 days after last systemic or local drug administration or 10 times the half life of the respective drug (except hormonal contraceptives)
• blood donation within the last two months
• blocking period due to another clinical study with investigational products; however at least 4 weeks after the end of the study or 10 times the half life of the respective drug
• lack of willingness or inability to co-operate adequately
• HIV and HBV and drug screening positive or not performed (in case of a positive HIV-test, the volunteers must be informed by a physician in a personal conversation)
• lactation and pregnancy test positive or not performed