Tolvaptan is a prescription drug used to treat… Hyponatremia (low sodium levels). It works by blocking the effects of hormones that cause the body to retain water and salt, which helps restore normal sodium levels in the body. Tolvasca is available in tablet form and should be taken with food for best results. You can buy this medicine online from our website with a valid prescription from your doctor. Tolvasca is a safe and effective way to treat the symptoms of hyponatremia.