Pharmacokinetics of non‐prescription sympathomimetic agents

Abstract

The pharmacokinetics of non-prescription sympathomimetic agents are discussed with respect to absorption from the gastrointestinal tract, volumes of distribution, metabolism and renal excretion. Where specific data are not available, postulations are made with inference from the chemical structures of these agents, or from studies with other drugs. No studies on hypertensive patients have been found, but attempts are made to correlate any possible changes in the pharmacokinetics of these sympathomimetic agents to hypertensive patients as a high proportion of the elderly population is hypertensive. Sympathomimetic agents with lesser polar hydroxl groups, for example, are thought to be more lipophilic and are more readily absorbed from the gastrointestinal tract, have higher volumes of distribution, and are more extensively metabolized. Major metabolic pathways include oxidation, deamination, demethylation, and conjugation. Most of these agents are excreted primarily through the kidneys and due to their basic nature, the rate of excretion is dependent on urinary pHs. Any alteration in kidney functions such as in the aged is, therefore, expected to have some clinical significance on the pharmacokinetics of these agents.

Occupational Contact Dermatitis Due to Acrylates and Methacrylates

“…The twice daily dose tablet had a T max between 3.8 and 6.1 h and the 24 h tablet had a T max of 11.87 h (Kanfer et al 1993). The onset of action is seen in 30 min (Chua et al 1989). Phenylephrine has a bioavailability of 38 %.…”

“…An active metabolite, norpseudoephedrine, is formed from N-demethylation (Chua et al 1989;Kanfer et al 1993). After 24 h post administration, 43-96 % of the parent compound can be recovered in the urine.…”