PETN stands for Pentaerythritol tetranitrate. It's in the nitrate family of explosives, closely related chemically to nitroglycerin, only more powerful. PETN is one of the most powerful conventional explosives known and is one of the two main ingredients used in plastic explosives such as Semtex. Like its cousin nitroglycerin, PETN is also used as a vasodilator drug to treat certain heart conditions, such as management of angina (chest pain).