In recent years, pharmaceutical cocrystals as a new solid
form
have received considerable attention among the applied novel methods
for modifying drug substance characteristics. Crystal engineering
offers an excellent opportunity to improve physicochemical and pharmacokinetic
properties such as solubility, dissolution rate, permeability, bioavailability,
biochemical/physical stability, etc. Application of the cocrystal
form in the pharmaceutical industry and in academia is becoming a
popular method to overcome solubility disadvantages of the active
pharmaceutical ingredient (API). Due to manipulation of the API crystalline
structure by cocrystal formation, solubility is not the only affected
property; some other properties of the newly produced solid form must
be considered to fulfill the desired therapeutic efficacy. The stability
of the cocrystal in solution is one of these influential features.
Regarding the aqueous nature of the gastrointestinal tract, unwanted
solution-mediated phase transformation of a cocrystal to a more stable
form causes inefficient drug delivery. It may potentially reduce the
drug concentration in the circulation. Cocrystal transformation products
could be a different polymorph, hydrated form, or mixture of the API
and coformer. This review focuses on the solution stability of cocrystals
and the effects of various factors such as polymers, surfactants,
biorelevant media, organic solvents, and pH.