Nitroglycerin, a common drug used for cardiac conditions, is utilised by medical personnel to minimise the risk of pulmonary edema and to reduce hypertension.[16] Antihistamines may be of benefit for pain relief,[17] but most cases require intravenous opioid analgesia. Fentanyl or morphine are usually chosen. Pethidine (meperidine, brand name Demerol in the US) should be avoided, as large doses are often required for pain relief and in this situation significant adverse effects from the pethidine metabolite norpethidine may occur.[18]