Melting point phase diagrams of free base and hydrochloride salts of bevantolol, pindolol and propranolol

Abstract

The crystalline nature of β-adrenergic antagonist racemates was characterized by differential scanning calorimetry. Melting point phase diagrams were prepared for the free base and hydrochloride salt forms of bevantolol, pindolol and propranolol. The free base form of bevantolol and propranolol behaved as a racemic compound with pseudoracemate character in the vicinity of the racemic mixture. Eutectics were found near the pure enantiomers and at the racemic mixture. The hydrochloride salt forms of these drugs were classified as conglomerates, possesing a eutectic in the diagram only at the racemic mixture. The diagram for free base pindolol revealed a pseudoracemate; a diagram for its hydrochloride salt was not feasible. Calculated initial and final melting temperatures adequately described experimental results for conglomerate, racemic compound and pseudoracemate examples.