Drug metabolism, routes

The renal clearance can be under estimated in the case of renal drug metabolism. The total drug clearance depends on bioavailability. Therefore, the most reliable estimate for the fraction eliminated by the renal route (fren) is given by the normal clearance (Clnorm) and drug clearance in case of acute and/ or chronic renal failure (Clfail), or from half-lives (Tl/2norm) and (Tl/2fail). 

In addition, other drugs such as alosetron (2), cyproheptadine (12), diazepam (13) or tamoxifen (49) are AT-demethylated by various microorganisms as a major metabolic route. The carboxylic acid resulting from the oxidative cleavage of the piperidine ring of phencyclidine (36), probably proceeding through an... 

For exogenous compounds such as drugs, various enzymes involved in both phase I and phase II metabolic routes are present, e.g. various isoforms of cytochrome p450, cytochrome b5, glucuronyl transferase and sulfotransferase [15]. 

Drugs metabolized by COMT Administer drugs known to be metabolized by COMT (ie, isoproterenol, epinephrine, norepinephrine, dopamine, dobutamine, methyidopa, apomorphine, isoetherine, bitolterol) with caution in patients receiving entacapone regardless of the route of administration (including inhalation), as their interaction may result in increased heart rates, arrhythmias, and excessive changes in blood pressure. 

Drug Active Metabolites Onset of Action Rate of Elimination Primary Metabolic Route... 

The alveolar-capillary membrane is normally very thin, has a huge surface area, and a large blood supply. Drugs given by this route, such as bronchodilators and pulmonary steroids, are rapidly absorbed into the bloodstream. This is also the route for administering the inhalational anaesthetics. DRUG METABOLISM AND EXCRETION... 

In species where reabsorption of drugs from the gastrointestinal tract increases the half-life of elimination, salivary secretion represents another important excretion route. The large volume of alkaline saliva produced by ruminants offers the possibility of trapping the acidic drugs. Exhalation of products of drug metabolism, such as carbon dioxide and water, can also account for drug excretion. 

There are other examples in which chirality is a factor in determining which particular metabolic route occurs, such as the metabolism of the drugs propranolol, metoprolol, and warfarin. 

---