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Drug Interactions between Seroquel XR and thioridazine

This report displays the potential drug interactions for the following 2 drugs:

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Interactions between your drugs

Major

thioridazine QUEtiapine

Applies to: thioridazine and Seroquel XR (quetiapine)

CONTRAINDICATED: Thioridazine can cause dose-related prolongation of the QT interval. Theoretically, coadministration with other agents that can prolong the QT interval including other antipsychotic agents may result in additive effects and increased risk of ventricular arrhythmias. Thioridazine treatment alone has been associated with several reported cases of torsade de pointes and sudden death.

Coadministration with thioridazine may decrease the plasma concentrations of quetiapine. The mechanism of interaction is unknown. In one study, thioridazine (200 mg twice a day for 8.5 days) administered to patients stabilized on quetiapine (300 mg twice a day) resulted in decreases in mean quetiapine peak plasma concentration (Cmax), systemic exposure (AUC) and trough plasma concentration (Cmin) by 47%, 40% and 31%, respectively. Quetiapine oral clearance (Cl/F) increased by 68%. Patients in the study reported increases in dizziness, insomnia, and dry mouth during coadministration, while sedation and prolonged sleep duration became worse in more than 25% of the patients. This is consistent with additive anticholinergic and CNS-depressant effects of these agents. Excessive anticholinergic effects can also result in paralytic ileus, hyperthermia, heat stroke, and the anticholinergic intoxication syndrome. Peripheral symptoms of anticholinergic intoxication commonly include mydriasis, blurred vision, flushed face, fever, dry skin and mucous membranes, tachycardia, urinary retention, and constipation. Central symptoms may include memory loss, disorientation, incoherence, hallucinations, psychosis, delirium, hyperactivity, twitching or jerking movements, stereotypy, and seizures. Other adverse effects that may be increased with this combination include orthostatic hypotension, extrapyramidal symptoms, and tardive dyskinesia.

MANAGEMENT: The concurrent use of thioridazine with other medications that can prolong the QT interval is considered contraindicated.

References

  1. Stadnyk AN, Glezos JD (1983) "Drug-induced heat stroke." Can Med Assoc J, 128, p. 957-9
  2. Mann SC, Boger WP (1978) "Psychotropic drugs, summer heat and humidity, and hyperplexia: a danger restated." Am J Psychiatry, 135, p. 1097-100
  3. Warnes H, Lehmann HE, Ban TA (1967) "Adynamic ileus during psychoactive medication: a report of three fatal and five severe cases." Can Med Assoc J, 96, p. 1112-3
  4. Sarnquist F, Larson CP Jr (1973) "Drug-induced heat stroke." Anesthesiology, 39, p. 348-50
  5. Johnson AL, Hollister LE, Berger PA (1981) "The anticholinergic intoxication syndrome: diagnosis and treatment." J Clin Psychiatry, 42, p. 313-7
  6. Lee BS (1986) "Possibility of hyperpyrexia with antipsychotic and anticholinergic drugs." J Clin Psychiatry, 47, p. 571
  7. Moreau A, Jones BD, Banno V (1986) "Chronic central anticholinergic toxicity in manic depressive illness mimicking dementia." Can J Psychiatry, 31, p. 339-41
  8. (2001) "Product Information. Seroquel (quetiapine)." Astra-Zeneca Pharmaceuticals
  9. (1997) "Quetiapine for schizophrenia." Med Lett Drugs Ther, 39, p. 117-8
  10. Potkin SG, Thyrum PT, Alva G, Bera R, Yeh C, Arvanitis LA (2002) "The safety and pharmacokinetics of quetiapine when coadministered with haloperidol, risperidone, or thioridazine." J Clin Psychopharmacol, 22, p. 121-30
View all 10 references

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Drug and food interactions

Moderate

thioridazine food

Applies to: thioridazine

GENERALLY AVOID: Concurrent use of ethanol and phenothiazines may result in additive CNS depression and psychomotor impairment. Also, ethanol may precipitate dystonic reactions in patients who are taking phenothiazines. The two drugs probably act on different sites in the brain, although the exact mechanism of the interaction is not known.

MANAGEMENT: Patients should be advised to avoid alcohol during phenothiazine therapy.

References

  1. Lutz EG (1976) "Neuroleptic-induced akathisia and dystonia triggered by alcohol." JAMA, 236, p. 2422-3
  2. Freed E (1981) "Alcohol-triggered-neuroleptic-induced tremor, rigidity and dystonia." Med J Aust, 2, p. 44-5

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Therapeutic duplication warnings

Therapeutic duplication is the use of more than one medicine from the same drug category or therapeutic class to treat the same condition. This can be intentional in cases where drugs with similar actions are used together for demonstrated therapeutic benefit. It can also be unintentional in cases where a patient has been treated by more than one doctor, or had prescriptions filled at more than one pharmacy, and can have potentially adverse consequences.

Duplication

Antipsychotics

Therapeutic duplication

The recommended maximum number of medicines in the 'antipsychotics' category to be taken concurrently is usually one. Your list includes two medicines belonging to the 'antipsychotics' category:

  • Seroquel XR (quetiapine)
  • thioridazine

Note: In certain circumstances, the benefits of taking this combination of drugs may outweigh any risks. Always consult your healthcare provider before making changes to your medications or dosage.

See also

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Drug Interaction Classification

These classifications are only a guideline. The relevance of a particular drug interaction to a specific individual is difficult to determine. Always consult your healthcare provider before starting or stopping any medication.
Major Highly clinically significant. Avoid combinations; the risk of the interaction outweighs the benefit.
Moderate Moderately clinically significant. Usually avoid combinations; use it only under special circumstances.
Minor Minimally clinically significant. Minimize risk; assess risk and consider an alternative drug, take steps to circumvent the interaction risk and/or institute a monitoring plan.
Unknown No interaction information available.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

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