2. Dissolution testing
• A dissolution method should have adequate discriminatory
power to detect formulation changes that affect the dissolution
rate of a drug product.
• Dissolution testing is an important tool for characterizing the
performance of oral solid dosage forms.
• Its significance is based on the fact that for a drug to be
effective, it must first be released from the product and dissolve
in the gastrointestinal fluids before absorption into the
bloodstream can happen.
• In other words, the rate and extent of drug absorption are
determined by its dissolution from the dosage form.
3. Problems
• Various equipment and operating variables are associated with
dissolution testing.
• The centering and alignment of paddle is critical in paddle
method.
• Turbulence can create increased agitation, resulting in higher
dissolution rate.
• Wobbling and tilting due to worn equipment should be
avoided.
4. • The basket method is less sensitive to tilting effect.
• However, the basket method is more sensitive to clogging due
to gummy materials.
• Pieces of small particles can also clog up the basket screen and
create a local non-sink condition for dissolution.
5. • Dissolved gas in the medium may form air bubbles on the
surface of the dosage form unit and can affect dissolution in
both the basket and paddle methods.
• For many drug products, the dissolution rates are higher with
the paddle method.
• Dissolution results at 50 rpm with the paddle method may
be equivalent to dissolution at 100rpm with the basket
method.
6. Example :
• In a study of sustained release Theophylline tablet compressed
at various degree of hardness,
Cameron et.al (1983) found that,
At 50rpm dissolution with the paddle method was faster than
that of basket method for tablets of 4.0kg hardness.
• However, with the tablets of 6.8kg hardness, similar
dissolution profile where obtained at 125rpm for basket and
paddle methods over a period of 6hrs.
• With both methods, increased dissolution rates where
observed where the rate were increased.
7. • Apparently, the composition of the formulation as well as,
process variables in manufacturing may both be important.
• No simple correlation can be made for dissolution results
obtained with different methods.
• In a comparison of the paddle and basket method in evaluating
a sustained release pseudoephedrine, guaifenesin preparation
Masih et.al (1983) found that the paddle method was more
discreminating in demonstrating dissolution differences among
drug products.
8. • At 100rpm, the basket method failed to pick up formulation
differences detected by paddle method.
• In the absence of invivo data, the selection of the dissolution
method is based on the type of drug product to be tested
• For eg.
low density preparation may be poorly wetted in the basket
method.
A gummy preoaration may clog up the
basket method.
9. A floating dosage form (eg. Suppositories) may be placed in a
stainless steel coil so that the dosage form remains at the
bottom of dissolution flask.
For many drugs, a satisfactory dissolution test may be
obtained with more than one method by optimizing the testing
condition.
