Quetiapine - Adverse Effects

Adverse Effects

The most common side-effect of quetiapine is somnolence. Other common side-effects include: sluggishness, fatigue, dry mouth, sore throat, dizziness, abdominal pain, constipation, upset stomach, orthostatic hypotension, inflammation or swelling of the sinuses or pharynx, blurred vision, increased appetite, and weight gain.

Uncommon side effects include bruises and disturbance in speech and language. Mouth ulcers are a rare side effect. Very rare side effects reported were rapid swelling of the skin around the eyes, which increased the appearance of skin ageing.

There is an emerging controversy regarding quetiapine fatalities. The deaths of at least six U.S. military veterans who were given drug cocktails including quetiapine have been attributed to its inclusion by military doctors to treat PTSD. Approximately 10,000 lawsuits against AstraZeneca for problems ranging from slurred speech and chronic insomnia to death have been filed by individuals from civilian populations.

It is marketed as one of the most sedating of all anti-psychotics, although those claims are contested. Beginning users may feel extremely tired and 'out of it' for the first few days, and sometimes longer. Quetiapine's newest indication, for bipolar depression, usually specifically calls for the entire dose to be taken before bedtime due to its sedative effects. The sedative effects may disappear after some time on the drug, or with a change of dosage, and with possibly different, non-sedative side-effects emerging.

Both typical and atypical antipsychotics can cause tardive dyskinesia. According to one study, rates are lower with the atypicals at 3.9% as opposed to the typicals at 5.5%. Although Quetiapine and Clozapine are atypical antipsychotics, switching to these atypicals is an option to minimize symptoms of tardive dyskinesia caused by other atypicals.

Weight gain can be a problem for some patients. Quetiapine has been found to cause more weight gain than fluphenazine, haloperidol, loxapine, molindone, olanzapine, pimozide, risperidone, thioridazine, thiothixene, trifluoperazine, and ziprasidone, but less than chlorpromazine, clozapine, perphenazine, and sertindole when calculated according to a fixed effects model.

Studies conducted on beagles have resulted in the formation of cataracts. While there are reports of cataracts occurring in humans, controlled studies including thousands of patients have not demonstrated a clear causal association between quetiapine therapy and this side-effect. However, the Seroquel website still recommends users have eye examinations every six months.

As with some other anti-psychotics, quetiapine may lower the seizure threshold, and should be taken with caution in combination with drugs such as bupropion.

A recent comparative study of anti-psychotics drugs has found that quetiapine mono treatment was associated with increased risk of death relative to the other analyzed treatments (but still better than no anti-psychotics drug treatment at all).