Seroquel (quetiapine)


Whilst atypical antipsychotics are similarly efficacious in treating both the positive and negative symptoms of schizophrenia and the symptoms of bipolar mania, their tolerability profiles differ [1,2]

Extrapyramidal symptoms (EPS)
EPS are a recognised side effect of antipsychotic medication.  The incidence of EPS (including akathisia) with Seroquel is similar to placebo in patients with schizophrenia [3] or bipolar mania [4]; and short- and long-term improvements in EPS were seen in a combined analysis of the open-label extension phase of four Phase IIIa multicentre, randomised, double-blind trials of Seroquel monotherapy in patients with schizophrenia. [5]

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Prolactin levels
Some antipsychotics, such as haloperidol and risperidone, are associated with increases in prolactin levels [6] which may in turn lead to sexual dysfunction and also increase the risk of osteoporosis [7].  However, data from a 6-week, randomised, double-blind, placebo-controlled trial in patients with schizophrenia demonstrated that the effect of Seroquel across its entire dose range on plasma prolactin levels is comparable with placebo in patients with schizophrenia [3].

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Benefits relating to quality of life measures
In a 6-month, open-label extension, Canadian multicentre study examining long-term patient satisfaction with Seroquel, a 7-item questionnaire carried out by the study investigators assessed patients’ satisfaction with, and acceptability of, long-term treatment.  Results from the questionnaires indicated that there were high levels of satisfaction and acceptability, and improved quality of life, following 6 months of treatment with Seroquel in patients with schizophrenia or schizoaffective disorder [8].

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In a 6-week, multicentre, double-blind, placebo-controlled trial, of 361 patients with schizophrenia the incidence of somnolence was similar in all treatment groups across the full dose range and in most cases the somnolence was mild and transient [3]  All cases of somnolence occurred within the first 3 weeks of treatment with Seroquel; in contrast, new cases were reported throughout the 6-week trial in the placebo group [3,9]

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Data from the pooled analysis of two twelve-week double-blind, randomised, placebo controlled studies of Seroquel monotherapy in 403 patients with bipolar mania showed that somnolence was significantly higher in Seroquel-treated patients than in those who received placebo (16.3% vs 4.0%, respectively; p<0.001).  The majority of these cases were mild to moderate in severity (97.1%) and somnolence was not a cause for discontinuation [10]

Tolerability conclusions for Seroquel

  • In the short- and long-term in patients with schizophrenia, Seroquel is associated with continuing improvements in EPS [5]

  • The effect of Seroquel across it entire dose range on plasma prolactin levels is comparable to placebo in patients with schizophrenia [3]

  • Seroquel is associated with benefits in aspects of quality of life in patients with schizophrenia [8]

  • The somnolence which occurs with Seroquel in patients with schizophrenia is usually mild and is not often persistent; in patients with bipolar mania, somnolence is generally mild to moderate and generally does not cause withdrawal [3,9]

  • The most common adverse events (incidence of ≥5%) in acute, placebo-controlled studies (Seroquel, n=719; placebo, n=404) in patients with schizophrenia (6 weeks) or bipolar mania (12 weeks) were:
    • Somnolence (18% vs 8% in placebo group)
    • Dizziness (11% vs 5% in placebo group)
    • Dry mouth (9% vs 3% in placebo group
    • Constipation (8% vs 3% in placebo group)
    • Serum gamma glutamyl transpeptidase increased (5% vs 1% in placebo group)
    • Weight gain (5% vs 1% in placebo group)
    • Dyspepsia (5% vs 1% in placebo group) [11]

Please note that the Prescribing Information will vary from country to country and should be checked before use.


  1. McIntyre RS, Konarski JZ. Tolerability profiles of atypical antipsychotics in the treatment of bipolar disorder. J Clin Psychiatry 2005; 66 Suppl 3: 28-36.
  2. Vieta E, Goikolea JM. Atypical antipsychotics: newer options for mania and maintenance therapy. Bipolar Disord 2005; 7 Suppl 4: 21-33.
  3. Arvanitis LA, Miller BG, the Seroquel Trial 13 study group. Multiple fixed doses of "Seroquel" (quetiapine) in patients with acute exacerbation of schizophrenia: a comparison with haloperidol and placebo. Biol Psychiatry 1997; 42: 233-246.
  4. Nasrallah HA, Brecher M, Paulsson B. Placebo-level incidence of extrapyramidal symptoms (EPS) with quetiapine in controlled studies of patients with bipolar mania. Bipolar Disord 2006; 8: 467-474.
  5. Kasper S, Brecher M, Fitton L, Jones AM. Maintenance of long-term efficacy and safety of quetiapine in the open-label treatment of schizophrenia. Int Clin Psychopharmacol 2004; 19: 281-289.
  6. Zhang XY, Zhou DF, Cao LY, Zhang PY, Wu GY, Shen YC. Prolactin levels in male schizophrenic patients treated with risperidone and haloperidol: a double-blind and randomized study. Psychopharmacology (Berl ) 2005; 178: 35-40.
  7. Halbreich U, Kinon BJ, Gilmore JA, Kahn LS. Elevated prolactin levels in patients with schizophrenia: mechanisms and related adverse effects. Psychoneuroendocrinology 2003; 28 Suppl 1: 53-67.
  8. Chue P, Abouelnasr W, Gendron A. An open-label effectiveness study of long-term quetiapine treatment. The Journal of Applied Research 2005; 5: 246-252.
  9. AstraZeneca Data on file. Seroquel is associated with a low incidence of somnolence during the early phase of treatment (first 7 days) which does not increase across the dose range, and infrequently results in withdrawal. 2001.
  10. Vieta E, Mullen J, Brecher M, Paulsson B, Jones M. Quetiapine monotherapy for mania associated with bipolar disorder: combined analysis of two international, double-blind, randomised, placebo-controlled studies. Curr Med Res Opin 2005; 21: 923-934
  11. AstraZeneca. Seroquel US prescribing information. Available at 2006.


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