"A decoction of samphire (crethmum) relaxes the bowels, brings away urine and humors from the kidneys; as does the powder of dried water plantain [alcima] taken in wine...." (Pliny, Natural HistoryXXVI.83)
The Romans followed the Greeks in the belief that a disease was caused by an imbalance among the body's four humors: blood, phlegm, yellow bile, and black bile. Wellness meant the humors were in harmony; sickness implied a disharmony in the humors' blend, with phlegm and bile considered the usual culprits. Food, though a necessity, was regarded as a primary source of disease, because inadequate digestion could result in the build-up of harmful residues within the body.
Thus, the logical treatment for any disease would be: (i) bleeding, to get rid of the excess of a misbehaving humor; (ii) starvation, to prevent the troubling humor from re-establishing itself; and (iii) purging, to remove any possible residual bad humors still lurking somewhere in the body. So wine's most common role in Roman medicine was as a vehicle with a pleasing taste that could mask the bitterness of say a diuretic prepared from the roots of sorrel, or a concoction of dried rue leaves mixed with a strong wine that would take away a woman's menstruation pains.