Transdermal properties of pet deworming thermosensitive sustained-release drops enhanced by hydroxypropyl methyl cellulose E5

Using hydroxypropyl methyl cellulose (HPMC E5) as a key excipient, a thermosensitive sustained-release drop formulation of imidacloprid (IMD) and moxidectin (MOX) was prepared. The effects of HPMC E5 on the thermosensitivity, rheology and transdermal behavior were investigated. Poloxamer 407 and 188 were used as thermosensitive matrices, and HPMC E5 served as a stabilizer and penetration auxiliary. 1,2-Propanediol, polyethylene glycol 400 and azone were used as penetration enhancers. The formulation was optimized via in vitro rat skin transdermal experiments, and the optimal ratios of P407, P188 and HPMC E5 were 12.0%, 3.5% and 0.5%, respectively. Infrared spectroscopy indicated hydrogen bonding between HPMC E5, the drug and the matrix. Rheological studies showed that HPMC E5 improved shear-thinning and thermosensitive gelation, enabling rapid film formation at body temperature and sustained drug release. Compared with the formulation without HPMC E5, addition of 0.5% HPMC E5 increased cumulative transdermal amounts of IMD and MOX to 0.62 and 0.45 mg cm −2 (P < 0.01), with good sustained-release characteristics. The skin irritation test revealed no redness or edema. HPMC E5 enhances transdermal absorption, sustained release, rheological adaptability and skin adhesion. The prepared drops avoid drug loss, reduce dosing frequency, and offer a safe, effective transdermal option for pet deworming.