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PharmD clinical pharmacy program Level 3, Semester 2 Biopharmaceutics & Pharmacokinetics (PT608(

3. Salivary Excretion

• The pH of saliva varies from 5.8 to 8.4.

• Unionized lipid soluble drugs are excreted passively.

• The bitter after taste in the mouth of a patient is indication of drug excreted in

saliva.

• Some basic drugs inhibit saliva secretion and are responsible for mouth dryness.

• Examples of compounds excreted in saliva are caffeine, phenytoin,

theophylline.

• In some instances, salivary secretion is responsible for localized side effects For

example:

• Excretion of antibiotics may cause black hairy tongue, gingival hyperplasia can

be a side effect of phenytoin.

4. Pulmonary Excretion

• The lung is the major organ of excretion for gaseous and volatile substances.

• Volatile drugs, such as gaseous anesthetics or drugs with high volatility are

excreted via the lungs into expired air.

• They are absorbed through lungs by simple diffusion Intact gaseous drugs are

excreted but not metabolites.

• Alcohol which has high solubility in blood and tissues are excreted slowly by lungs.

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