a-t 2016; 47: 40

ABUSE OF THE ANTIHISTAMINES DIPHENHYDRAMINE AND DIMENHYDRINATE

The French National Agency for Medicines and Health Products Safety ANSM has issued a warning about the abuse of the antihistamines diphenhydramine (DPH; e.g. EMESAN) and dimenhydrinate (e.g. VOMEX A) (1), which is a molecular compound of diphenhydramine and 8-chlorotheophylline. During the period from 2003 to May 2014, French pharmacovigilance centres received 59 corresponding reports related primarily to overuse, abuse and dependence. These cases predominantly involved male adolescents and young adults (with an average age of 33) (2).

The potential for the abuse of diphenhydramine and dimenhydrinate has been known for several years (3,4). Numerous experience reports on "DPH trips" and "EMESAN trips" can be found in online forums on "legal drugs". Taking antihistamines together with alcohol can increase and change their effect in unpredictable ways (5). In some cases, diphenhydramine and dimenhydrinate are taken together with other drugs, such as dextromethorphan (e.g. SILOMAT DMP), a cough suppressant that made headlines because of dependence and criminal abuse as long as 50 years ago (a-t 1998; No. 2: 27-8).

The two H1-antihistamines are highly sedative, approved as sleeping medication and antiemetics and are available over the counter. Typical overdose symptoms are anticholinergic effects including mydriasis, dry mouth and skin, fever, seizures, tachycardia and cardiac arrhythmia. High doses, such as 250 mg or 300 mg (6) also have a stimulating effect on the central nervous system, producing euphoria and changes in perception including auditory and visual hallucinations. There is currently no reliable data on the scope of this abuse in order to determine whether the over-the-counter-sale of these drugs is still justified. However, the fact that more than 100 reports of suicide attempts in connection with diphenhydramine are currently being recorded annually in the Adverse Drug Reaction Database of the German Federal Institute for Drugs and Medical Devices (BfArM) (7) indicates that there is an additional problem that further speaks against the over-the-counter-sale, -Ed.