Optimizing Particle Size of pH Modifiers Enhances Dissolution of Weakly Basic Drugs.

Area of Science:

• Pharmaceutical Sciences
• Drug Delivery Systems
• Physical Chemistry

Background:

• Carvedilol, a BCS Class II drug, exhibits pH-dependent solubility.
• Understanding dissolution is crucial for optimizing drug formulation and bioavailability.
• Citric acid is explored as a dissolution enhancer for weakly basic drugs.

Purpose of the Study:

• To investigate the pH-dependent dissolution of carvedilol.
• To examine the influence of citric acid concentration and particle size on carvedilol release.
• To elucidate the role of microenvironmental pH modification in drug dissolution.

Main Methods:

• Dissolution studies were performed across a simulated gastrointestinal pH range (1.2-7.8).
• The effects of citric acid concentration (3% and 9%) and particle size (fine vs. coarse) were evaluated.
• Microenvironmental pH was monitored to assess its impact on drug solubility.

Main Results:

• Carvedilol solubility was high and unaffected by citric acid particle size at low pH (1.2-1.6).
• Fine citric acid particles created an acidic microenvironment (pH 3.5±0.2) in the mid-pH range (3.8-6.5), enhancing carvedilol solubility and dissolution.
• The particle size effect was less pronounced at higher citric acid concentrations and diminished at high pH (6.8-7.8).

Conclusions:

• Citric acid concentration universally improved carvedilol dissolution.
• The particle size of citric acid significantly impacts carvedilol release in a pH-dependent manner.
• Coarse citric acid particles demonstrated a sustained release effect at higher pH values.