Evaluation of the physicochemical stability of creams containing hydroquinone 5% manipulated in pharmacies in Conselheiro Lafaiete, Minas Gerais

Abstract

Hydroquinone is currently the most prescribed topical  depigmenting agent for treating skin hyperpigmentation.
By inhibiting melanin synthesis, hydroquinone is responsible for reducing the production of skin pigment.
Formulations containing this active ingredient face  challenges regarding their chemical stability, particularly
due to susceptibility to oxidation, which can affect their efficacy and even pose toxicity risks to patients. Given
this instability, this study aimed to evaluate the physicochemical stability of formulations obtained from three compounding pharmacies in the municipality of Conselheiro Lafaiete, Minas Gerais. The methodology  involved analyzing the labeling, packaging, organoleptic and physicochemical characteristics of the formulations
stored at a temperature of 8 ± 2 ºC and 75% humidity for 90 days. The labeling of the formulations lacked some information required by current legislation, particularly concerning usage warnings. Only formulation C was stored in appropriate packaging (aluminum). Regarding pH, all formulations met the recommended standard. However, all formulations exhibited a reduction in viscosity, indicating instability during the study period, as this parameter can affect the release rate of the active ingredient. The formulations from pharmacy A showed lower spreadability compared to the other creams. In summary, the compounding pharmacies did not meet the stability parameters for the formulations. Additionally, none satisfactorily included the mandatory warnings on the labeling, which may influence storage conditions and promote hydroquinone oxidation. It is concluded that some of the analyzed parameters need to be reassessed, particularly concerning labeling and packaging of the formulations, to ensure consumers receive safe, effective, and higher-quality products.