title: Assessment of the physical properties and stability of mixtures of tetracycline hydrochloride ointment and acyclovir cream.
abstract: In dermatology, ointments are often mixed as part of drug therapy, but mixing often leads to incompatibility. Three combinations of tetracycline ointment (TC-o) and acyclovir cream (ACV-cr) were prepared at a TC-o:ACV-cr ratio of 1:1 using a brand-name ACV-cr and two generic ACV-cr (samples TC-o+ACV-A, TC-o+ACV-B, and TC-o+ACV-C). Microscopic examination revealed separation in TC-o+ACV-C. Viscosity and elasticity measurement indicated that the storage modulus (G') and loss modulus (G″) of each of the TC-o+ACV-cr mixtures behaved similarly to those of an ACV-cr and the loss tangent (tanδ) behaved similarly to that of a TC ointment. In addition, differences in the storage modulus (G') and loss modulus (G″) of the TC-o+ACV-cr mixtures were noted. To assess stability, each TC-o+ACV-cr mixture was stored away from direct sunlight at 25 °C and an RH of 84% and at 4 °C (in a refrigerator). HPLC revealed that the ACV content in each TC-o+ACV-cr mixture remained at 95-105% for up to 14 days under both sets of storage conditions. A decline in TC content in each TC-o+ACV-cr mixture was not noted with storage at 4 °C but was noted over time with storage at 25 °C and an RH of 84%. In addition, significant differences in the percent decline in TC content in each TC-o+ACV-cr mixture occurred with storage at 25 °C and an RH of 84%. Thus, differences in physical properties and stability may occur when combining brand-name and generic drugs, and temperature and humidity may be the cause of the TC-o's incompatibility.
authors: Laboratory of Drug Safety Management, Faculty of Pharmaceutical Sciences, Josai University, 1-1 Keyakidai, Sakado-shi, Saitama 3500295, Japan. yinoue@josai.ac.jp
authors: Yutaka
authors: Y
authors: Inoue
authors: Kayoko
authors: K
authors: Furuya
authors: Rikimaru
authors: R
authors: Maeda
authors: Isamu
authors: I
authors: Murata
authors: Ikuo
authors: I
authors: Kanamoto
mesh_terms: D000212:Acyclovir / Q000737:chemistry*; D004338:Drug Combinations; D004355:Drug Stability; D004356:Drug Storage; D004548:Elasticity; D006863:Hydrogen-Ion Concentration; D009824:Ointments; D013752:Tetracycline / Q000737:chemistry*; D014783:Viscosity; D014867:Water / Q000032:analysis
chemical_list: D004338:Drug Combinations; D009824:Ointments; D014867:Water; D013752:Tetracycline; D000212:Acyclovir