Nitroglycerin is available in tablets, ointment, solution for intravenous use, transdermal patches, or sprays administered sublingually. Some forms of nitroglycerin last much longer in the body than others. Continuous exposure to nitrates has been shown to cause the body to stop responding normally to this medicine. Experts recommend that the patches be removed at night, allowing the body a few hours to restore its responsiveness to nitrates. Shorter-acting preparations of nitroglycerin can be used several times a day with less risk of developing tolerance. Nitroglycerin was first used by William Murrell to treat angina attacks in 1878, with the discovery published that same year.