Diazepam must first be released from the oil phase of the emulsion before it can exert a therapeutic effect. In fact, peak blood levels of diazepam are reached only after 15 minutes following i.v. injection of Diazemuls and after 2 hours following i.m. administration. Subsequent to a rapid distribution phase, diazepam undergoes a longer elimination phase, which varies with age, from approximately 20 hours at age 20 to approximately 80 hours at age 80. The desmethyl metabolite has an elimination half-life of 50 to 120 hours. Diazepam and its metabolites are excreted mainly in the urine, as glucoronides or sulfates.
Diazepam crosses the placenta and is secreted in breast milk.
Diazemuls should not be administered to patients in shock or coma. There have been rare reports of apnea or cardiac arrest, usually following i.v. administration, especially in elderly or very ill patients and in those with limited pulmonary reserve. Resuscitative equipment including that necessary to support respiration should therefore be readily available. Since lingual obstruction of the airway may occur, particularly in children and in the elderly, caution is required to maintain a free airway in patients receiving Diazemuls injection. Rapid injection or the use of veins with too small a lumen carries the risk of thrombophlebitis.