Medication Overview

Fluoxetine is a selective serotonin reuptake inhibitor (SSRI) commonly used in the treatment of major depressive disorder, obsessive-compulsive disorder, bulimia nervosa, and panic disorder. The medication modulates serotonin levels in the brain, helping to improve mood, emotions, and sleep patterns.

Mechanism of Action

Fluoxetine operates by inhibiting the reuptake of serotonin into the presynaptic neuron, leading to increased serotonin availability in the synaptic cleft. This action enhances serotonergic neurotransmission in the central nervous system.

Dosage Forms

Fluoxetine is available in several dosage forms, including oral tablets, capsules, delayed-release capsules, and liquid solutions. These various formats provide flexibility for patient-specific needs and preferences.

Indications for Use

Fluoxetine is indicated for major depressive disorder, obsessive-compulsive disorder, bulimia nervosa, and panic disorder. It is also used off-label for conditions such as certain anxiety disorders and premenstrual dysphoric disorder.

Prescribing Information

The starting dose for adults with major depressive disorder typically begins at 20 mg daily. For obsessive-compulsive disorder, the dose can range from 20 to 60 mg per day. In bulimia nervosa, the effective dose is often 60 mg daily. For panic disorder, the initial dose usually starts at 10 mg daily, with a gradual increase to 20 mg after one week.

Pharmacokinetics Profile

After oral administration, Fluoxetine is well absorbed, with peak plasma concentrations occurring within 6 to 8 hours. The elimination half-life ranges from 1 to 4 days for fluoxetine, and 7 to 15 days for its active metabolite norfluoxetine. Because of this long half-life, fluoxetine can remain active in the system for weeks after discontinuation.

Metabolism and Excretion

Fluoxetine undergoes extensive hepatic metabolism mainly via the cytochrome P450 enzyme CYP2D6. The drug and its active metabolite norfluoxetine are excreted primarily in the urine.

Drug Interactions

Fluoxetine can interact with numerous medications due to its inhibition of CYP2D6. It may enhance the effects of anticoagulants, leading to an increased risk of bleeding. Concurrent use with monoamine oxidase inhibitors (MAOIs) can result in serious interactions, including serotonin syndrome.

Contraindications List

Fluoxetine is contraindicated in patients with hypersensitivity to the drug. It should not be used concurrently with MAOIs or thioridazine due to the risk of severe drug interactions. Use is also contraindicated in patients undergoing pimozide treatment.

Adverse Reactions

Common adverse reactions of Fluoxetine include nausea, insomnia, somnolence, headache, anxiety, and dizziness. Gastrointestinal disturbances such as diarrhea and dry mouth are also frequently reported. In some cases, fluoxetine can cause weight loss and sexual dysfunction.

Special Populations Guidelines

Dosage adjustments may be necessary for elderly patients or those with hepatic impairment, given the potential for altered pharmacokinetics in these groups. Pediatric use in certain indications has been approved but requires careful monitoring for efficacy and safety.

Pediatric Considerations

In children and adolescents, Fluoxetine is approved for treating major depressive disorder and obsessive-compulsive disorder. Doses typically start lower than adult doses and should be adjusted based on clinical response and tolerability.

Pregnancy and Lactation

Fluoxetine can cross the placenta and is excreted into breast milk. The use of fluoxetine during pregnancy may present risks, including potential complications for the neonate. Assessing the risk-benefit ratio is crucial for pregnant or breastfeeding individuals.

Overdose Management

Symptoms of fluoxetine overdose may include nausea, vomiting, agitation, and seizures. In the event of overdose, immediate medical attention is required. Supportive care and symptom management are primary treatments, with the potential use of activated charcoal if ingestion is recent.

Patient Monitoring

Routine monitoring includes assessment of clinical symptoms, adherence to the medication regimen, and potential side effects. For long-term users, periodic evaluation of liver function and other relevant laboratory parameters is recommended.

Withdrawal Symptoms

Discontinuation of fluoxetine should be gradual to avoid withdrawal symptoms such as mood swings, irritability, agitation, dizziness, and sensory disturbances. Because of fluoxetine’s longer half-life, tapering off may be more extended compared to other SSRIs.

Storage Guidelines

Store Fluoxetine at room temperature, away from moisture and heat. Ensure that the medication is stored in a secure location out of reach of children and pets. It is essential to dispose of unused medication properly, following local regulations.

Pharmacodynamic Properties

Fluoxetine’s pharmacodynamic effects include mood elevation, reduced symptoms of anxiety and panic, and decreased frequency of bulimic episodes. These therapeutic benefits are primarily mediated through serotonergic modulation.

Patient Counseling Points

Patients should be informed about the potential side effects, the importance of adherence to prescribed dosages, and avoiding sudden discontinuation. Counseling about the possibility of interactions with other medications and alcohol is also vital.

Treatment Duration

The duration of fluoxetine treatment varies based on the condition being treated and the patient’s response. For depression, a period of 6 to 12 months may be necessary, while long-term therapy might be required for chronic conditions like OCD.

Clinical Efficacy Studies

Numerous clinical trials have demonstrated the efficacy of fluoxetine in treating major depressive disorder, obsessive-compulsive disorder, and bulimia nervosa. These studies typically show improvements in mood, reduced compulsive behaviors, and decreased binge/purge episodes.

Common Side Effects

The common side effects include gastrointestinal symptoms like nausea and diarrhea, as well as central nervous system effects such as insomnia, headache, and dizziness. Many side effects diminish with continued use.

Critical Precautions

Patients with a history of seizures, bipolar disorder, or bleeding disorders require careful monitoring during fluoxetine therapy. It is also essential to regularly assess the risk of suicidal ideation, especially when initiating or changing dosages.