Frågedatum: 2005-08-31
RELIS database 2005; id.nr. 21922, DRUGLINE
www.svelic.se
Utredningen som riktar sig till hälso- och sjukvårdspersonal, har utformats utefter tillgänglig litteratur och resurser vid tidpunkten för utredning. Innehållet i utredningen uppdateras inte. Hälso- och sjukvårdspersonal är ansvarig för hur de använder informationen vid rådgivning eller behandling av patienter.


Are there any known pharmacological interactions between hydroxyzine (Atarax) and risperidone (Risp



Fråga: Are there any known pharmacological interactions between hydroxyzine (Atarax) and risperidone (Risperdal)? Anxiolytic treatment with hydroxyzine is contemplated in a patient already medicating with risperidone.

Sammanfattning: There are no reports of an interaction between hydroxyzine and risperidone. Theoretically, concomitant use could increase the risk of cardiac arrhythmias, sedation and nausea and if hydroxyzine is instated, therapeutic drug monitoring of risperidone could be recommended.

Svar: No reports of an interaction between hydroxyzine and risperidone were found in Drugline, Medline or standard pharmacological literature.

A double-blind placebo-controlled trial in 19 psychotic patients (1) indicates that hydroxyzine impairs the therapeutic response to phenothiazines and a reference book on drug interactions suggest that this interaction could be generalized to antipsychotics in general (2). However, the small study size, the use of multiple outcome variables and the pooling of several different antipsychotics (chlorpromazine, trifluoperazine and thioridazine) make the result less liable. Furthermore, the unknown interaction mechanism makes it difficult to judge the applicability to risperidone treatment.

Hydroxyzine is primarily a histamine H1-antagonist with some anticolinergic effects (3), while risperidone has antagonistic effects on serotonin 5HT2-, dopamine D2- and alfa1-adrenergic receptors and a low affinity for H1 receptors (4). Hence, there is no obvious risk of a direct agonistic or antagonistic interaction on the receptor level.

Both hydroxyzine and risperidone cause prolongation of the cardiac QTc interval (5,6). Hence, co-medication with the two drugs may increase the risk of ventricular arrhythmias. Furthermore, hydroxyzine inhibits the main enzyme involved in risperidone metabolism, cytochrome P450 2D6 (CYP2D6) (7). The 9-hydroxylated risperidone metabolite formed by CYP2D6 is pharmacologically active and differences in CYP2D6 activity is of disputable importance for the over-all pharmacologic effect. Nevertheless, a low CYP2D6 activity has been mentioned as a possible risk factor for risperidone-related QT prolongation (6).

Sedation and nausea are common side effects of both hydroxyzine and risperidone (3,4), and the risk may be further increased in co-medication.

Referenser: