Page 107 - Interactive Theoritical Notes of Bioharmaceutics and pharamcokinetics.docx compressed

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

1. For some hydrophobic drugs, micronization and other dry particle size-

reduction can result in aggregation of the material (due to increased surface

static charges) e.g.: aspirin

2. For drugs such as penicillin G and erythromycin, which are unstable in gastric

fluids, their chemical degradation will be minimized if they remain in the solid

state.

3. Administration of nitrofurantoin as a finely divided solid may cause gastric

irritation more than when taken as coarse particles.

(b) Crystal form (Polymorphism- Amorphous solids- Solvates)

 Many drugs can exist in more than one crystalline form, this property is referred to

as polymorphism.

 Each crystalline form is known as a polymorph.
 Different polymorphs are characterized by having different physicochemical

properties.

 Only one crystalline form is stable and other forms are converted to this form.

 When the conversion is slow, the polymorph is said to be metastable and can be

used in dosage forms (it shows poorly organized crystal, weakly bonded).

 A metastable polymorph usually exhibits a greater dissolution rate than the

corresponding stable polymorph.

 The metastable form of a poorly soluble drug exhibit increased bioavailability

compared to the stable form.

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