The antibiotic minocycline, and the compound creatine, which is produced in muscle tissue, could slow the progress of Parkinson's disease.
The compounds may help by reducing cellular stress and inflammation.
Research is still in its initial state, but a study of 200 patients with early-stage Parkinson's showed that those who were given the substances seemed to decline less rapidly than those who were given a placebo.
About 1.5 million Americans suffer from Parkinson's disease, a neurological ailment that causes tremors, stiff or frozen limbs, slow movement, and impaired balance.