This comprehensive review explores two antiretroviral drugs, Etravirine (ETV) and Darunavir (DRV), a non-nucleoside reverse transcriptase inhibitor and a protease inhibitor, that are commonly used in human immunodeficiency virus (HIV) infection treatment, often in combination with each other. The pharmacokinetic properties of these drugs are covered as well as the clinical trials of these two drugs combined. This paper also delves into the possible repurposing of these two drugs for other diseases, with drug repurposing being a significant factor in addressing global health challenges. DRV was extensively studied for treating COVID-19, as well as other infections, such as candidiasis and cryptococcosis, while ETV proved to be efficient in hampering Zika virus brain infection. The focus on cancer repurposing is also explored, with the results revealing that ETV has a particular inhibitory effect on ovarian cancer in vitro and on cancer molecules, such as anterior gradient protein 2 homolog (AGR2) and casein kinase 1 (CK1ε), and that DRV has an in silico inhibitory effect on human lactate dehydrogenase A (LDHA) and induces the in vitro and in vivo inhibition of pepsin, consequent laryngopharyngeal reflux, and possible laryngeal and hypopharyngeal carcinomas. The significance of fresh methods of drug development is emphasized in this work, as is the enormous potential for new therapeutic uses of the antiretroviral drugs ETV and DRV in viral and non-viral disorders.