BMA Concise Guide to Medicine & Drugs

Quetiapine

Brand name Seroquel

Used in the following combined preparations None

QUICK REFERENCE

Drug group Antipsychotic drug

Overdose danger rating Medium

Dependence rating Low

Prescription needed Yes

Available as generic Yes

GENERAL INFORMATION

Quetiapine is an atypical antipsychotic drug that is prescribed for the treatment of schizophrenia as well as for mania and depression in bipolar affective disorder (manic-depression). It can be used to treat “positive” symptoms (thought disorders, delusions, and hallucinations) and “negative” symptoms (blunted affect and emotional and social withdrawal in schizophrenia).

Elderly people excrete the drug up to 50 per cent more slowly than the usual adult rate. They, therefore, need to be prescribed much lower doses in order to avoid adverse effects.

INFORMATION FOR USERS

Your drug prescription is tailored for you. Do not alter dosage without checking with your doctor.

How taken/used Tablets.

Frequency and timing of doses 2 x daily.

Adult dosage range Schizophrenia 50mg daily (starting dose). Mania 100mg daily (starting dose). The dose is increased over several days (both). Usual range is 300–450mg daily, maximum 750mg daily (schizophrenia); 800mg (mania).

Onset of effect 1–7 days.

Duration of action Up to 12 hours.

Diet advice Avoid grapefruit juice, because it may increase blood levels of quetiapine and the drug’s effects.

Storage Keep in original container at room temperature out of the reach of children.

Missed dose Take as soon as you remember. If your next dose is due within 4 hours take a single dose now and skip the next.

Stopping the drug Do not stop the drug without consulting your doctor; symptoms may recur.

Exceeding the dose An occasional unintentional extra dose is unlikely to cause problems. Large overdoses may cause unusual drowsiness, palpitations, and low blood pressure. Notify your doctor.

POSSIBLE ADVERSE EFFECTS

Unusual drowsiness, weight gain, indigestion, constipation, dizziness, and fainting are common adverse effects of quetiapine. Discuss with your doctor if you experience dizziness or fainting or if the other effects are severe. Less commonly, the drug may cause a stuffy nose, sore throat, or palpitations. Consult your doctor if any of these occur. Long-term use of quetiapine may rarely cause abnormal movements and increase the risk of certain disorders (seeProlonged use).

INTERACTIONS

Anti-epileptics Quetiapine may oppose the effect of these drugs. However, phenytoin and carbamazepine may also reduce the effects of quetiapine.

Sedatives All drugs that have a sedative effect on the central nervous system are likely to increase the sedative properties of quetiapine.

Erythromycin, clarithromycin, ketoconazole, and fluconazole These drugs may increase the effects of quetiapine.

Grapefruit juice may increase the blood levels and effects of quetiapine.

Protease inhibitors These drugs for HIV/AIDS may increase the blood levels and effects of quetiapine.

SPECIAL PRECAUTIONS

Be sure to tell your doctor if:

· You have epilepsy.

· You have diabetes.

· You have liver or kidney problems.

· You have heart problems.

· You are taking other medicines.

Pregnancy Safety not established. Discuss with your doctor.

Breast-feeding Safety not established. Discuss with your doctor.

Infants and children Not recommended.

Over 60 Reduced doses necessary. The elderly eliminate quetiapine more slowly than younger adults.

Driving and hazardous work Avoid such activities until you have learned how quetiapine affects you; the drug can cause drowsiness.

Alcohol Avoid. Alcohol increases the sedative effects of this drug.

PROLONGED USE

Prolonged use of quetiapine may rarely cause tardive dyskinesia, in which there are involuntary movements of the tongue and face. There is also an increased risk of developing diabetes and raised blood lipid levels. With long-term use in elderly patients, quetiapine also carries a greater risk of stroke than some other antipsychotic drugs.