Frågedatum: 2001-10-15
RELIS database 2001; id.nr. 17803, DRUGLINE
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Is it advisable to initiate sibutramine (Reductil) treatment in a patient who is on methadone, cita



Fråga: Is it advisable to initiate sibutramine (Reductil) treatment in a patient who is on methadone, citalopram, diclofenac and alimemazine medication: possible interactions?

Sammanfattning: At present, there is limited information in the literature regarding sibutramine and reported interactions with other drugs. Sibutramine could theoretically interact with all of the questioned drugs above. The interaction with SSRI:s is the most important since serotonin syndrome is a severe and life threatening condition. Coadministration of sibutramine and citalopram should therefore be avoided. In this patient, sibutramine treatment is not advisable even if citalopram is withdrawn.

Svar: Sibutramine was introduced on the Swedish market only recently (April 2001). In USA 3.5 million patients have been treated since the introduction 1998. In the literature, so far, there are no reports on sibutramine and interactions with the above mentioned drugs. However, sibutramine, being a serotonin, noradrenalin, and dopamine reuptake inhibitor could increase the risk of serotonin syndrome if given concurrently with any of the SSRI:s eg citalopram (1,2).

Furthermore, sibutramine and methadone are mainly metabolised by the same cytochrome P450 isoenzyme CYP3A4 (3,4), thus, metabolic interactions must be considered. Theoretically, pharmacodynamic interactions must also be taken into consideration since methadone, like morphine, also acts on the dopamine system. The clinical significance of this is difficult to evaluate. However, the combination of sibutramine with other agents that affect the central nervous system has not been systematically evaluated and therefore warrants caution (1).

Alimemazine is an antihistamine and sedative with anticholinergic effects eg dry mouth and obstipation. These side-effects are also common for sibutramine and the outcome could be more pronounced side-effects (4).

It is known that sibutramine to minor extent is metabolised by the same cytochrome P450 isoenzyme as diclofenac (CYP2C9) but there is no clinical data on interactions.

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