Advances in drug delivery: improved bioavailability and drug effect.

Alterations in drug delivery produce substantial changes in the bioavailability of anticholinergic agents. These bioavailability differences change the efficacy and tolerability of this drug class, which consistently enhances patient compliance and overall drug effect. In order for drug delivery to alter successfully the bioavailability of a specific agent, the metabolism of that agent and the effect of the degradatory pathway on drug-parent compound levels need to be established. This will enable researchers to design improved or altered delivery pathways to maximize the benefits of these agents. Intestinal metabolism is known to affect certain agents, specifically oxybutynin chloride. Therefore, delivery techniques have been designed that either substantially lower or totally bypass intestinal (presystemic) metabolism. These alternate paths include extended-release oral, cutaneous, intravesical, and intravaginal routes. In addition, improvements in drug delivery have also been found to influence positively efficacy and tolerability profiles associated with tolterodine tartrate, another anticholinergic agent. A long-acting oral formulation has been shown to increase drug efficacy while decreasing tolerability concerns and side effects such as xerostomia. These salubrious effects are, in part, due to the more stable serum-drug concentrations that are imparted by this long-acting formulation.