Physico-chemical characterisation of different clindamycin phosphate samples

Area of Science:

• Pharmaceutical Sciences
• Materials Science
• Physical Chemistry

Background:

• Pharmaceutical powders, primarily in solid-state, interact with liquids and vapors during production.
• Variations in chemically identical active pharmaceutical ingredients (APIs) and excipients from different suppliers can lead to unpredictable interactions.
• These variations influence both manufacturing processes and the final pharmaceutical product's properties, necessitating material characterization.

Purpose of the Study:

• To determine and compare the physico-chemical properties of three clindamycin phosphate powder samples from different suppliers.
• To identify potential differences that could explain variable physical stability observed in aqueous solutions.
• To correlate specific properties with the observed recrystallization behavior of one sample during storage.

Main Methods:

• Characterization of three clindamycin phosphate powder samples (S(1), S(2), S(3)) obtained from distinct suppliers.
• Determination of surface free energy components using the Wu and the Good-van Oss methods.
• Analysis of surface morphology, thermal behavior (melting points, onset temperatures), and peak width.

Main Results:

• Significant differences were observed in surface free energy, surface morphology, and thermal behavior among the clindamycin phosphate samples.
• All samples exhibited monopolar, electron-acceptor (Lewis acid) characteristics, with sample S(3) showing stronger acidic behavior.
• Sample S(3) displayed a wider melting point onset peak and was found to recrystallize in aqueous solution during storage, unlike S(1) and S(2).

Conclusions:

• The physico-chemical differences, particularly surface free energy and thermal behavior (melting point peak width), explain the variable stability of clindamycin phosphate powders.
• The stronger Lewis acid character and wider melting peak of sample S(3) are linked to its recrystallization tendency.
• Sample S(1) is identified as the preferred choice for formulating stable pharmaceutical dosage forms due to its favorable properties and lack of recrystallization.