Here's what rhymes with painkilling.

Consider these alternatives

cortisone / shown tranquilizing / rising lidocaine / procaine antipsychotic / logic immunosuppressant / present retroviral / antiretroviral antiretroviral / retroviral anesthetic / magnetic valium / alien infusions / institutions curare / their rheological / logical hallucinogenic / academic corticosteroids / steroids psychotropic / logic