Preliminary Findings in Switching from Parenteral Haloperidol to Oral Quetiapine Treatment in the Management of Acutely Agitated Patients

Agitation is a very common but complex clinical challenge to the hospital psychiatrist. A subset of agitated patients, threatening their life and that of others, unresponsive to verbal interventions, has to be medicated by parenteral administration. For this indication haloperidol is a well studied and routinely prescribed compound despite its limiting side effects. Therefore, switching to 2^nd generation antipsychotics after successful treatment of the acute symptoms should be considered. Our prospective naturalistic study describes clinical practice in the management of acutely agitated patients. Fifteen acute agitated psychiatric patients requiring i.v. haloperidol treatment at admission were subsequently switched to oral quetiapine, remaining on this medication until their discharge. Age, gender, weight, diagnoses, dosages of haloperidol and quetiapine, serum concentration analysed by HPLC, duration of i.v. application, smoking behaviour and co-medications were registered. The patients (10 f) were mainly affected by schizophreniform (N=8), affective or schizoaffective (N=6) disorders. The mean age was 38.4 years (25–58), the mean body weight 71.2kg (55–103.5). Eight patients were identified as smokers. Haloperidol was prescribed for a mean duration of 5.8 days (2–11) in a mean dose of 24.6mg (15–30) reaching a mean serum concentration of 19.9 ng/ml (6–47) with a mean C/D ratio of 0.8 (0.3–1.57). Switching to quetiapine was based on clinical improvement. The mean dose of quetiapine was 573.3mg (300–800) resulting in a mean serum concentration of 267.6 ng/ml (57–520) and a mean C/D ratio of 0.5 (0.1–0.9). A subanalysis revealed that patients (N=8) initially treated with high doses of haloperidol (up to 30mg) were switched earlier to quetiapine (average 2 days) and discharged with smaller doses quetiapine of 525mg/d (300–800) than patients (N=7) medicated with haloperidol up to 20mg requiring a mean quetiapine doses of 671.5mg/d (500–800). Additionally smokers showed lower haloperidol but higher quetiapine serum concentration than non smokers. Since significantly more smokers were present in the group treated with high haloperidol doses, the opposite effects of nicotine on haloperidol and quetiapine will be discussed. Our results indicate that the initial dose of parenteral haloperidol has a clinical impact on the switching time to quetiapine and on the final doses of quetiapine.