PHAR 4634 - Chapter 7 Page 3

Buccal/Sublingual

Some drugs are taken as smaller tablets which are held in the mouth or under the tongue. These are buccal or sublingual dosage forms. 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. Nicotine containing chewing gum may be used for cigarette smoking replacement.

Advantages:

First pass - The liver is by-passed thus there is no loss of drug by first pass effect for buccal administration. Bioavailability 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 is inconvenient. If any is swallowed that portion must be treated as an oral dose and subject to first pass metabolism.

Small doses only can be accommodated easily.

Rectal

Most commonly by suppository or enema. Some drugs given by this route include aspirin, theophylline, chlorpromazine and some barbiturates

Advantages:

By-pass liver - Some of the veins draining the rectum lead directly to the general circulation, thus by-passing the liver. Reduced first-pass effect.

Useful - This route may be most useful for patients unable to take drugs orally or with younger children.

Disadvantages:

Erratic absorption - Absorption is often incomplete and erratic. However for some drugs it is quite useful. There is research being conducted to look at methods of improving the extent and variability of rectal administration.

Not well accepted.

This page was last modified: 12 February 2001