FLOXIL 20mg

Indications

• Major depressive disorder
• Obsessive-compulsive disorder
• Bulimia nervosa
• Panic disorder
• Premenstrual dysphoric disorder
• Generalized anxiety disorder

Dosage

Children: Refer to the BNF for Children for specific dosing guidelines.

Adults: Refer to the BNF for specific dosing guidelines.

Mechanism of action

Fluoxetine selectively inhibits the reuptake of serotonin (5-HT) by blocking the serotonin transporter (SERT). This leads to increased concentrations of serotonin in the synaptic cleft, enhancing serotonergic neurotransmission. The drug also has a metabolite, norfluoxetine, that contributes to its pharmacological effects.

Pharmacodynamics

Fluoxetine's primary action is the modulation of serotonin levels in the brain, which is associated with mood regulation. The increased serotonin availability is thought to improve mood and alleviate symptoms of depression and anxiety. The onset of therapeutic effects may take several weeks, as adaptive changes in neurotransmitter systems occur.

Pharmacokinetics

Fluoxetine is well absorbed orally and has a bioavailability of approximately 60%. It undergoes extensive hepatic metabolism via cytochrome P450 enzymes, primarily CYP2D6, leading to the formation of its active metabolite, norfluoxetine. The elimination half-life of fluoxetine is about 4 to 6 days, while norfluoxetine has a half-life of 7 to 15 days, allowing for once-daily dosing. Fluoxetine and its metabolites are excreted predominantly in urine.

Contra-indications

• Hypersensitivity to fluoxetine or any component of the formulation
• Concurrent use of monoamine oxidase inhibitors (MAOIs)
• Use in patients with a history of serotonin syndrome

Adverse effects

• Nausea
• Insomnia
• Anxiety
• Headache
• Dizziness
• Diarrhea
• Sexual dysfunction
• Weight changes
• Increased sweating
• Tremors

Interactions

• Increased risk of serotonin syndrome with other serotonergic drugs
• Possible interaction with anticoagulants, increasing bleeding risk
• May enhance effects of other CNS depressants
• Potential interaction with drugs metabolized by CYP2D6

Precautions

• Monitor for worsening depression or emergence of suicidal thoughts
• Use cautiously in individuals with a history of seizures
• Assess for potential hypomanic or manic episodes in patients with bipolar disorder
• Consider risk of withdrawal symptoms upon abrupt discontinuation

Pregnancy

Fluoxetine should only be used during pregnancy if the potential benefit justifies the potential risk to the fetus. It is associated with potential risks including neonatal withdrawal syndrome.

Breast-feeding

Fluoxetine is excreted in breast milk. The effects on the nursing infant should be considered, and monitoring for adverse effects is recommended.

Storage

Store at room temperature, away from light and moisture. Keep out of reach of children.

Formulations

• Capsules
• Tablets
• Oral solution