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.
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
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.
- Filtration = unbound drug is passively filtered by the glomerulus.
- Secretion = drug is actively secreted.
- Reabsorption = drug is passively reabsorbed back into the blood.
Effects on respiration, cardiovascular system
Evaluated in vitro
Cell based systems for genotoxicity
Assessed in animals in Acute and chronic studies
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