Design of fipronil and praziquantel drops using hydroxypropyl methyl cellulose E5 with superior release and penetration.

The design of a superior release and penetration of fipronil (FPN) and praziquantel (PZQ) drops holds significant importance in the simultaneous deworming of pets both in vitro and in vivo. Herein, the application of 1,2-propanediol, azone, hydroxypropyl methyl cellulose E5 (HPMC E5) and anhydrous ethanol as osmotic promoters was investigated, with the primary objective of enhancing the drug's release and permeability. Dosages of 1,2-propanediol, azone, HPMC E5 and anhydrous ethanol were screened based on in vitro drug release and transdermal testing. The optimal prescription for the FPN and PZQ drops was obtained by using 9-11 % 1,2-propylene glycol, 69-70 % anhydrous ethanol, and 0.1-0.15 % HPMC E5. The addition of HPMC E5 can increase the in vitro cumulative release of drops and improve drug penetration into the skin. The optimal PZQ and FPN drops presented safe skin irritation, and should be stored away from strong light and high temperature.