Tadalafil-malonic acid cocrystal : Physicochemical characterization, pH-solubility and supersaturation studies

• The purpose of this study was to enhance the solubility and dissolution of a poorly water-soluble drug, tadalafil (TDF), by cocrystal formation with malonic acid (MOA), to characterize the cocrystal structure, and to quantify the cocrystal solution behavior. The crystal structure revealed a 1:1 stoichiometry wherein the TDF molecules form a double layered structure through N–H…O=C interactions linked to a catemeric chain of MOA molecules via O-H…O hydrogen bonds. Cocrystal solubility advantage (SA defined as Scocrystal/Sdrug) or supersaturation index was determined from eutectic point measurements to be 102 to 129 in the pH range of 1 to 3. Cocrystal dissolution generated supersaturation levels (Cmax/Sdrug) of 30 in buffer and 120 in the presence of a nucleation inhibitor, HPMC. The amorphous form of TDF generated supersaturation 3 times lower than cocrystal in buffer, and not significantly different from cocrystal in the presence of HPMC. Thus, supersaturation index is a valuable metric for assessing the risk of cocrystal conversion during kinetic studies and for predicting conditions when the usage of a precipitation inhibitor may significantly increase cocrystal exposure levels.

Ämnesord

MEDICIN OCH HÄLSOVETENSKAP  -- Hälsovetenskap -- Annan hälsovetenskap (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Health Sciences -- Other Health Sciences (hsv//eng)

NATURVETENSKAP  -- Kemi -- Fysikalisk kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences -- Physical Chemistry (hsv//eng)

Nyckelord

Health Science

Hälsovetenskap

Chemistry of Interfaces

Gränsytors kemi

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