Author's reply

We appreciate Dr. Engfer's comments on our paper, and would like to make a few concluding remarks.

First, our paper was written in 1997 - 1998 and submitted in April 1998. Cases published after 1998 could therefore only be considered in part. We even included some non-English, non-German case reports of possibly lower quality, so we feel that every effort was taken to give a complete overview. In some other case reports, intoxication with new non-benzodiazepine hypnotics have been reported, but this cannot be automatically attributed to a possible zolpidem dependence.

Second, Dr. Engfer is right that the very interesting study by Glaeske has not to my knowledge been published in a proper form yet. We would like to encourage the authors to do this. Overall trends in prescription and consumption of psychotropic and other drugs have been given by Dr. Glaeske in the annual periodical, Jahrbuch Sucht, from the Deutsche Hauptstelle gegen die Suchtgefahren. Zolpidem (two drugs marketed) was the third hypnotic to be sold in 2.5 mil packages in 1999, with the other formulation ranking twelfth place [2]. Results of Prof Keup's “Frühwarnsystem” have been published regularly. Clinical study findings have consistently indicated that the use of zolpidem and other non-benzodiazepine hypnotics is very infrequent in drug users when compared to conventional benzodiazepines. Finally, the results of the Drug Commission of the German Medical Association (Arzneimittelkommission der deutschen Ärzteschaft) as cited in the publication are apparently not questioned by Dr. Engfer. A quick look at recent publications would clearly reveal that a number of other cases of zolpidem abuse and dependence have been published [1] [4] however, in their recent review, Holm and Goa concluded that “there is little evidence of tolerance to the hypnotic effects of zolpidem, or rebound insomnia or withdrawal symptoms after discontinuation of the drug when it is given as recommended. . .” [3]. So there is no or at least only a low apparent risk for some form of low-dose dependence as there is for benzodiazepines. In conclusion, we state that the evidence of abuse potential of zolpidem still is minor when compared to conventional hypnotics.

Future research may especially focus on the risk of intoxication and abuse potential of hypnotics in the elderly population, as recent data indicate a significant risk in this population [2].

References

• 1 Aragona M. Abuse, dependence and epileptic seizures after zolpidem withdrawal. Review and case report.  Clin Neuropharmacol. 2000;  23 281-283
• 2 Glaeske G. Psychotrope und andere Arzneimittel mit Missbrauchs- und Abhängigkeitspotential. In: DHS (ed) Jahrbuch Sucht 2001. Geestacht: Neuland 2000: 63-69
• 3 Holm K J, Goa K L. Zolpidem: an update of its pharmacology, therapeutic efficacy, tolerability in the treatment of insomnia.  Drugs. 2000;  59 865-889
• 4 Madrak L N, Rosenberg M. Zolpidem abuse.  Am J Psychiatry. 2001;  158 1330-1331

Correspondence