Steady-state serum concentrations of imipramine, its main metabolites and clinical response in primary enuresis

Clinical pharmacokinetics of drugs used to treat urge incontinence

Urge incontinence (also known as overactive bladder) is a common form of urinary incontinence, occurring alone or as a component of mixed urinary incontinence, frequently together with stress incontinence. Because of the pathophysiology of urge incontinence, anticholinergic/antispasmodic agents form the cornerstone of therapy. Unfortunately, the pharmacological activity of these agents is not limited to the urinary tract, leading to systemic adverse effects that often promote nonadherence. Although the pharmacokinetics of flavoxate, propantheline, scopolamine, imipramine/desipramine, trospium chloride and propiverine are also reviewed here, only for oxybutynin and tolterodine are there adequate efficacy/tolerability data to support their use in urge incontinence. Oxybutynin is poorly absorbed orally (2-11% for the immediate-release tablet formulation). Controlled-release oral formulations significantly prolong the time to peak plasma concentration and reduce the degree of fluctuation around the average concentration. Significant absorption occurs after intravesical (bladder) and transdermal administration, although concentrations of the active N-desethyl metabolite are lower after transdermal compared with oral administration, possibly improving tolerability. Food has been found to significantly affect the absorption of one of the controlled-release formulations of oxybutynin, enhancing the rate of drug release. Oxybutynin is extensively metabolised, principally via N-demethylation mediated by the cytochrome P450 (CYP) 3A isozyme. The pharmacokinetics of tolterodine are dependent in large part on the pharmacogenomics of the CYP2D6 and 3A4 isozymes. In an unselected population, oral bioavailability of tolterodine ranges from 10% to 74% (mean 33%) whereas in CYP2D6 extensive metabolisers and poor metabolisers mean bioavailabilities are 26% and 91%, respectively. Tolterodine is metabolised via CYP2D6 to the active metabolite 5-hydroxymethyl-tolterodine and via CYP3A to N-dealkylated metabolites. Urinary excretion of parent compound plays a minor role in drug disposition. Drug effect is based upon the unbound concentration of the so-called 'active moiety' (sum of tolterodine + 5-hydroxymethyl-tolterodine). Terminal disposition half-lives of tolterodine and 5-hydroxymethyl-tolterodine (in CYP2D6 extensive metabolisers) are 2-3 and 3-4 hours, respectively. Coadministration of antacid essentially converts the extended-release formulation into an immediate-release formulation. Knowledge of the pharmacokinetics of these agents may improve the treatment of urge incontinence by allowing the identification of individuals at high risk for toxicity with 'usual' dosages. In addition, the use of alternative formulations (controlled-release oral, transdermal) may also facilitate adherence, not only by reducing the frequency of drug administration but also by enhancing tolerability by altering the proportions of parent compound and active metabolite in the blood.

Enuresis and common voiding abnormalities

Voiding problems, and in particular nocturnal enuresis, can usually be evaluated and managed without resorting to complex procedures or invasive tests. A good history with attention to toilet habits and the possible presence of infection can help distinguish patients who may have significant organic pathologic conditions who require further investigation. Wetting alarms are effective with a low recidivism rate but are noisy. DDAVP is effective, works rapidly, and is discrete but has a higher recidivism rate. Treatment is aimed at correcting any poor toilet habits and using the appropriate alarm device or medication.

Antidepressant treatments in children and adolescents: II. Anxiety, physical, and behavioral disorders

Part II of this review critically evaluates antidepressants' (AD) efficacy in children and adolescents with anxiety, physical, and behavioral disorders as well as AD's side-effect spectrum. AD are administered increasingly to youths with specific anxiety syndromes phenomenologically paralleling those in adults which are responsive to AD (e.g., panic, obsessive-compulsive disorders). While several trials have not substantiated earlier theoretical considerations suggesting their usefulness in separation anxiety, their recent success in ameliorating obsessive-compulsive symptoms is encouraging. Systematic drug treatment studies however are limited because of the common overlap of anxiety syndromes with each other and other prominent psychiatric disturbances. More consistent benefits with AD are seen in the physical (e.g., enuresis, bulimia nervosa) and behavioral disorders (e.g., attention deficit-hyperactivity disorder). The wide-ranging benefits of AD in nonaffective disorders suggest AD are more appropriately viewed as broad spectrum pharmacotherapeutics.

The pharmacokinetics of tricyclic antidepressant drugs in the elderly

Antidepressants, especially tricyclic agents (TCAs), are increasingly used in geriatric patients since depression is a common mood disorder in the elderly and the size of elderly population is increasing. Notwithstanding the importance of kinetics to better use of drugs, its study in the elderly (regarding TCAs) is not sufficiently developed. The present paper briefly reviews the available data on amitriptyline, nortriptyline, protriptyline, imipramine, desipramine and clomipramine kinetics in the elderly.