Routes of drug administration给药途径.ppt

* * Routes of drug administration * * Objectives: To discuss the peculiar features of the various routes of drug administration ? To apply the advantages and disadvantages of the various routes of drug administration to optimize patient therapeutic benefit * * Buccal/Sublingual Buccal or sublingual dosage form enable drugs to be taken as smaller tablets held in the mouth or under the tongue. Buccal tablets are often harder tablets [4 hour disintegration time], designed to dissolve slowly. Nitroglycerin, as a softer sublingual tablet [2 min disintegration time] may be used for the rapid relief of angina. This ROA is also used for some steroids such as testosterone and oxytocin while nicotine-containing chewing gum may be used for cigarette smoking replacement. * * Advantages of buccal sublingual administration: First pass - The liver is by-passed thus there is no loss of drug by first pass effect for buccal administration. Bioavailability thus is higher. Rapid absorption - Because of the good blood supply to the area absorption is usually quite rapid. Drug stability - pH in mouth relatively neutral (cf. stomach - acidic). Thus a drug may be more stable. * * Disadvantages Holding the dose in the mouth may be inconvenient. If any is swallowed that portion must be treated as an oral dose and subject to first pass metabolism. Only small doses can be accommodated easily. * * Rectal Most commonly used for suppository or enema. Some drugs given by this route include aspirin, dipyrone, paracetamol, theophylline, chlorpromazine and some barbiturates * * Advantages of Rectal route By-pass liver - Some of the veins draining the rectum lead directly to general circulation, thus by-passing the liver. There is therefore reduced first-pass effect. Useful - This route may be most useful for patients unable to take drugs orally or with younger children. * * Disadvantages of rectal route Erratic absorption - Absorption is often incomplete and erratic. H