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

(C). Micellar Solubilization

 Micellar solubilization can increase the solubility of drugs in the GIT.

 Micelles are formed when the surfactant is present in concentration above CMC.

 Bile salts in the GIT are present above their CMC so they act as solubilizers for

slightly water-soluble drugs resulting in an increased bioavailability.

 The enhancement of drug absorption after meals is often related to the increased

bile flow which solubilize the drug molecules.

(D). Chemical stability of the drug in the GI fluids

Instability in GI fluids is usually caused by acidic or enzymatic hydrolysis.

Certain drugs like penicillin G and methicillin are hydrolyzed by the acidic medium

of the stomach (that is why they are given normally parenterally).

Other penicillins such as penicillin V and ampicillin are more stable in the acidic

PH of the stomach.

The concept of delaying the dissolution of a drug until it reaches the small intestine

has been employed to improve the bioavailability of erythromycin in the GIT.

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