Cytotoxic effects of opiate agonist loperamide hydrochloride on human oral cancer cells—an invitro study

Aim: Loperamide hydrochloride (HCl), a peripheral opioid receptor agonist primarily used as an antidiarrheal drug, has been reported to induce apoptosis in various cancer cell lines. However, its effects on oral cancer cells are yet to be ascertained. This study investigates the cytotoxic effects of loperamide HCl on oral squamous cell carcinoma (OSCC) cells, exploring its potential as a repurposed therapeutic agent. Methods: The OECM-1 OSCC cells were treated with various concentrations of loperamide HCl. The metabolic alterations of OECM-1 cells were spectrophotometrically assessed at 4, 24, 48, and 72 hours using the alamarBlue cell proliferation assay. The half-inhibitory concentration (IC50) of loperamide HCl on OECM-1 cells was calculated through non-linear regression analysis. Apoptosis was evaluated using the Caspase-3/7 assay. Results: Loperamide HCl suppressed OECM-1 cell proliferation after 24 hours. The IC50 values of loperamide HCl on OECM-1 cells were non-evaluable at 4 hours but progressively decreased to 80.82 µM at 24 hours, 37.69 µM at 48 hours, and 34.29 µM at 72 hours. Significant apoptosis was observed at loperamide HCl concentrations of 40 µM and 50 µM after 72 hours of treatment. Conclusions: Loperamide HCl demonstrates a time- and dose-dependent cytotoxic effect on OECM-1 cells, significantly inhibiting proliferation and inducing apoptosis at higher concentrations. The decreasing IC50 values over time indicate enhanced cytotoxicity with prolonged exposure. These findings suggest loperamide HCl’s potential as a therapeutic agent for OSCC.