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# TUSQ QD
## Overview
TUSQ QD is a once-daily oral medication containing **quetiapine fumarate**, an atypical antipsychotic.
## Primary Indications
* Treatment of schizophrenia.
* Adjunctive treatment of major depressive disorder (MDD).
* Treatment of bipolar I disorder (manic episodes, depressive episodes, and maintenance).
## Adult Dosing
* **Schizophrenia:** Initiate at 25 mg twice daily or 300 mg once daily (evening). Titrate dose gradually. Typical effective dose range: 300-450 mg/day in divided doses or once daily. Maximum: 800 mg/day.
* **Bipolar I Disorder (Manic Episodes):** Initiate at 100 mg twice daily or 300 mg once daily (evening). Titrate dose. Typical effective dose range: 400-600 mg/day in divided doses or once daily. Maximum: 800 mg/day.
* **Bipolar I Disorder (Depressive Episodes):** Initiate at 50 mg once daily (evening). Titrate dose. Typical effective dose: 300 mg once daily (evening). Maximum: 300 mg/day.
* **Adjunctive Treatment of MDD:** Initiate at 50 mg once daily (evening). Titrate dose. Typical effective dose: 150-300 mg once daily (evening). Maximum: 300 mg/day.
**Note:** For all indications, doses are typically advanced gradually. The "QD" in the drug name suggests a once-daily formulation; however, quetiapine is often initiated with twice-daily dosing and then transitioned to once-daily, especially in the evening, for maintenance therapy or when managing specific symptoms. Confirm the specific formulation and recommended titration schedule with the product monograph or local protocol.
## Pediatric Dosing
* **Schizophrenia (13-17 years):** Initiate at 50 mg twice daily. Titrate dose. Typical effective dose range: 300-450 mg/day. Maximum: 400 mg/day.
* **Bipolar I Disorder (10-17 years):**
* Manic Episodes: Initiate at 100 mg twice daily or 300 mg once daily (evening). Titrate dose. Typical effective dose range: 400-600 mg/day. Maximum: 600 mg/day.
* Depressive Episodes: Initiate at 50 mg once daily (evening). Titrate dose. Typical effective dose: 150-300 mg once daily (evening). Maximum: 300 mg/day.
**Note:** Pediatric dosing requires careful titration and monitoring due to increased risk of adverse effects like weight gain, metabolic changes, and extrapyramidal symptoms (EPS).
## Dose Adjustments
* **Hepatic Impairment:** Initiate at 25 mg once daily and titrate slowly. Dose may need to be reduced.
* **Concomitant Use with CYP3A4 Inhibitors (e.g., ketoconazole, itraconazole):** The dose of quetiapine should be increased up to three times the usual dose. If quetiapine is discontinued, reduce the quetiapine dose.
* **Concomitant Use with CYP3A4 Inducers (e.g., carbamazepine, phenytoin, rifampin):** The dose of quetiapine should be increased up to five times the usual dose. If quetiapine is discontinued, reduce the quetiapine dose.
## Contraindications
* Hypersensitivity to quetiapine or any excipients.
## Adverse Effects
Common: Somnolence, dizziness, dry mouth, weight gain, orthostatic hypotension, constipation, asthenia, abdominal pain, tremor, increased appetite.
Serious: Neuroleptic malignant syndrome (NMS), tardive dyskinesia (TD), hyperglycemia and diabetes mellitus, hyperlipidemia, cataracts, agranulocytosis, leukopenia, neutropenia, myocarditis, QT prolongation, suicidal thoughts and behaviors.
## Key Drug Interactions
* **CYP3A4 Inhibitors/Inducers:** See Dose Adjustments.
* **CNS Depressants (e.g., benzodiazepines, alcohol):** Additive CNS depressant effects.
* **Antihypertensives:** Additive hypotensive effect, especially orthostatic hypotension.
* **Dopaminergic Agents (e.g., Levodopa):** May antagonize the effects of levodopa.
* **Drugs known to prolong QT interval:** Increased risk of arrhythmias.
## Monitoring
* Baseline and periodic weight, BMI, waist circumference.
* Baseline and periodic fasting blood glucose and lipid profiles.
* Blood pressure, especially orthostatic vital signs.
* Signs and symptoms of NMS and TD.
* Complete blood counts, especially in patients with a history of low white blood cell count or drug-induced neutropenia/leukopenia.
* Ophthalmologic exams for cataracts.
* Suicidal ideation assessment.
## Clinical Pearls
* Quetiapine is generally associated with a lower risk of EPS compared to first-generation antipsychotics.
* Due to its long half-life and sedative properties, it is often administered once daily in the evening, particularly for maintenance therapy and depressive symptoms.
* Rapid titration can increase the risk of adverse effects, especially orthostatic hypotension and sedation.
* Consider a starting dose of 25 mg twice daily for elderly patients or those with hepatic impairment.
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**Disclaimer:** This information is intended for healthcare professionals and should not replace consultation with the official prescribing information and product monograph for TUSQ QD (quetiapine fumarate) or any other medication. Always verify current dosing, indications, contraindications, warnings, and precautions before prescribing or dispensing.
