Gyrex Film Coated Tablet 300 Mg

Gyrex Film Coated Tablet 300 mg is an antipsychotic medication containing quetiapine fumarate, manufactured by Santa Farma Pharmaceutical Company in Turkey. This comprehensive guide explores its composition, therapeutic applications, dosing recommendations, and safety profile to provide healthcare providers and patients with essential information about this medication.

Composition and Formulation

Each Gyrex Film Coated Tablet contains 300 mg of quetiapine base, equivalent to 345.39 mg of quetiapine fumarate. The tablet formulation includes several excipients including polyvinyl pyrrolidone, calcium hydrogen phosphate dihydrate, microcrystalline cellulose, sodium starch glycolate, lactose monohydrate (bovine-derived), magnesium stearate, hydroxypropyl methylcellulose, titanium dioxide, talc, and polyethylene glycol. These inactive ingredients help maintain the tablet’s integrity and facilitate proper absorption of the medication.

Therapeutic Uses

Quetiapine, the active ingredient in Gyrex, belongs to a class of medications known as atypical antipsychotics. It has received approval for multiple psychiatric conditions, making it a versatile treatment option in modern psychiatry.

Schizophrenia

Gyrex is indicated for the treatment of schizophrenia in adults and adolescents aged 13 years and older. Clinical trials have demonstrated its effectiveness in managing both positive symptoms (hallucinations, delusions) and negative symptoms (social withdrawal, lack of motivation) associated with schizophrenia. The medication helps stabilize thought processes and reduce the severity of psychotic episodes.

Bipolar Disorder

Quetiapine demonstrates significant efficacy across the spectrum of bipolar disorder:

Manic Episodes

Gyrex effectively treats moderate to severe manic episodes in bipolar I disorder, both as monotherapy and as an adjunctive treatment with mood stabilizers like lithium or divalproex. For adolescents aged 10-17 years with bipolar I disorder, Gyrex can also be used to manage manic episodes, though with specific dosing considerations.

Depressive Episodes

One of the distinguishing features of quetiapine is its efficacy in treating depressive episodes associated with bipolar I and II disorders. This dual action on both poles of bipolar disorder makes it particularly valuable in clinical practice.

Maintenance Treatment

Gyrex is indicated for preventing recurrence of manic or depressed episodes in patients with bipolar disorder who have previously responded to quetiapine treatment. This maintenance therapy helps stabilize mood and reduce the frequency of episodic fluctuations.

Major Depressive Disorder

As an adjunctive therapy to antidepressants, extended-release quetiapine formulations help manage symptoms of major depressive disorder in adults who have not responded adequately to antidepressant monotherapy.

Mechanism of Action

Quetiapine’s therapeutic effects stem from its complex interactions with multiple neurotransmitter systems in the brain. The medication has a strong affinity for serotonin 5-HT2 receptors and acts as an antagonist at dopaminergic D1 and D2 receptors.

The antipsychotic effects are primarily attributed to D2 receptor antagonism in the mesolimbic pathway, which helps reduce positive symptoms of schizophrenia. Additionally, quetiapine and its active metabolite norquetiapine demonstrate norepinephrine transporter inhibition and partial agonist activity at the 5-HT1A receptor, contributing to its anxiolytic and antidepressant properties.

Norquetiapine also shows affinity for histamine H1 receptors, various serotonergic receptors (5-HT1E, 5-HT2A, 5-HT2B, 5-HT7), muscarinic receptors (M1, M3, M5), and α1-adrenergic receptors, which explains some of the side effects associated with the medication.

Pharmacokinetics

Quetiapine demonstrates favorable pharmacokinetic properties that influence its clinical use. The medication is rapidly absorbed after oral administration, with peak plasma concentrations occurring within 1-2 hours. It exhibits linear pharmacokinetics within the clinical dose range, meaning that increases in dose produce proportional increases in plasma concentration.

The drug is approximately 83% bound to serum proteins and has a mean terminal half-life of approximately 7 hours. Quetiapine is primarily eliminated through hepatic metabolism, predominantly via the cytochrome P450 enzyme CYP3A4. Following administration, approximately 73% of the drug is excreted in urine and 21% in feces, with less than 1% excreted as unchanged quetiapine.

Dosage and Administration

Gyrex can be administered with or without food, and different dosing schedules exist for various indications.

Schizophrenia

For adults with schizophrenia, the recommended titration schedule is:

• Day 1: 50 mg daily (divided into two doses)

• Day 2: 100 mg daily (divided into two doses)

• Day 3: 200 mg daily (divided into two doses)

• Day 4: 300 mg daily (divided into two doses)

After initial titration, the maintenance dose typically ranges from 300-450 mg per day, though doses from 150-750 mg/day may be used depending on clinical response and patient tolerability.

Bipolar Disorder

Manic Episodes

For treatment of manic episodes in adults with bipolar disorder:

• Day 1: 100 mg daily (divided into two doses)

• Day 2: 200 mg daily (divided into two doses)

• Day 3: 300 mg daily (divided into two doses)

• Day 4: 400 mg daily (divided into two doses)

The dose may be further increased up to 800 mg/day by day 6, with adjustments not exceeding 200 mg/day.

Depressive Episodes

For bipolar depression, the recommended titration is:

• Day 1: 50 mg at bedtime

• Day 2: 100 mg at bedtime

• Day 3: 200 mg at bedtime

• Day 4 onwards: 300 mg at bedtime (maintenance dose)

Special Populations

Elderly Patients

Elderly patients should begin with a lower dose (50 mg/day) with more gradual titration to minimize the risk of adverse effects.

Hepatic Impairment

Patients with hepatic impairment should initiate treatment at 25 mg/day with gradual titration based on clinical response and tolerability.

Side Effects

Like all medications, Gyrex may cause various adverse reactions ranging from common and mild to rare but serious.

Common Side Effects

Frequently reported side effects include dizziness, sedation, drowsiness, dry mouth, constipation, weight gain, increased appetite, and headache. Many patients experience somnolence, particularly during the initial phase of treatment, which may diminish over time.

Serious Side Effects

More serious adverse reactions that require immediate medical attention include orthostatic hypotension (low blood pressure when standing), seizures, hyperglycemia (high blood sugar), tardive dyskinesia (abnormal involuntary movements), and neuroleptic malignant syndrome (a rare but potentially life-threatening condition characterized by fever, muscle rigidity, and autonomic instability).

Long-term use of quetiapine may lead to the development of cataracts, necessitating regular eye examinations.

Precautions and Warnings

Suicidality

There may be an increased risk of suicidal thoughts or behavior, especially at the beginning of treatment or during dose adjustments. Patients, particularly younger individuals, should be monitored closely for clinical worsening or unusual changes in behavior.

Elderly Patients with Dementia

Quetiapine is not approved for the treatment of dementia-related psychosis due to an increased risk of death in elderly patients with dementia.

Metabolic Changes

Quetiapine can cause metabolic changes including hyperglycemia, dyslipidemia, and weight gain. Regular monitoring of metabolic parameters is recommended, especially in patients with pre-existing metabolic disorders or risk factors.

Cardiovascular Considerations

Caution is advised in patients with cardiovascular disease, history of QT prolongation, or conditions that may increase the risk of arrhythmias.

Drug Interactions

CYP3A4 Inhibitors and Inducers

Co-administration with potent CYP3A4 inhibitors (such as ketoconazole or ritonavir) can significantly increase quetiapine exposure, requiring dose reduction. Conversely, CYP3A4 inducers (such as phenytoin, carbamazepine, or rifampin) can substantially decrease quetiapine levels, necessitating dose increases.

Other Significant Interactions

• Thioridazine: Increases clearance of quetiapine

• CNS depressants: May enhance CNS depression

• Antihypertensive agents: May potentiate hypotensive effects

Table of Essential Information

Conclusion

Gyrex Film Coated Tablet 300 mg represents an important therapeutic option in the management of several psychiatric disorders. As with any antipsychotic medication, individualized treatment approaches should consider the balance between efficacy and tolerability. Regular monitoring for metabolic changes, cardiovascular effects, and neurological symptoms is essential throughout treatment. Healthcare providers should work closely with patients to optimize dosing regimens and manage potential side effects to ensure the best possible outcomes.

When prescribed appropriately and monitored carefully, quetiapine can significantly improve quality of life for individuals suffering from schizophrenia, bipolar disorder, and treatment-resistant depression. Patient education regarding potential side effects, the importance of adherence, and regular follow-up appointments remains critical to successful treatment with Gyrex.