Half life of prozac
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Understanding the Half-Life of Prozac (Fluoxetine)
Introduction to Fluoxetine (Prozac)
Fluoxetine, commonly known by its brand name Prozac, is a widely used antidepressant belonging to the class of selective serotonin reuptake inhibitors (SSRIs). It is primarily prescribed for the treatment of major depressive disorder, obsessive-compulsive disorder, and other mood disorders 4.
Pharmacokinetics of Fluoxetine
Absorption and Bioavailability
Fluoxetine is well absorbed after oral administration, with a bioavailability of approximately 72% in dogs, which is indicative of its efficient absorption in humans as well 4. The time to reach maximum concentration (Tmax) in the bloodstream is between 4 to 8 hours 4.
Metabolism and Active Metabolite
Fluoxetine is metabolized in the liver to its active metabolite, norfluoxetine. Both compounds are potent inhibitors of serotonin reuptake, contributing to their therapeutic effects 14.
Half-Life of Fluoxetine
The half-life of fluoxetine varies depending on the duration of administration. After a single dose, the elimination half-life ranges from 1 to 3 days 4. However, with long-term administration, the half-life extends to an average of 4 days due to its nonlinear pharmacokinetics 4. This extended half-life allows for once-daily dosing, which improves patient compliance 3.
Half-Life of Norfluoxetine
Norfluoxetine, the active metabolite of fluoxetine, has a significantly longer half-life compared to its parent compound. The half-life of norfluoxetine ranges from 7 to 9 days 14. This prolonged half-life means that norfluoxetine remains in the bloodstream for an extended period, maintaining its therapeutic effects even after the parent drug has been eliminated 12.
Clinical Implications
Steady-State Concentrations
Due to the long half-lives of both fluoxetine and norfluoxetine, steady-state concentrations are achieved slowly, typically over several weeks of consistent dosing 2. This characteristic necessitates careful consideration when adjusting dosages to avoid accumulation and potential toxicity.
Side Effects and Toxicity
The side effects of fluoxetine primarily involve the central nervous system, including symptoms such as nervousness, tremor, and jitteriness 1. In neonates, fluoxetine toxicity can present with central nervous system symptoms and increased heart rate, although these effects tend to resolve as the drug is metabolized and eliminated 1.
Conclusion
Fluoxetine (Prozac) is a widely used antidepressant with a complex pharmacokinetic profile. Its half-life ranges from 1 to 4 days, extending with long-term use, while its active metabolite, norfluoxetine, has a half-life of 7 to 9 days. These long half-lives contribute to the drug's efficacy and convenience of once-daily dosing but require careful management to avoid accumulation and potential side effects. Understanding these pharmacokinetic properties is crucial for optimizing therapeutic outcomes and ensuring patient safety.
Sources and full results
Most relevant research papers on this topic
Fluoxetine hydrochloride (Prozac) toxicity in a neonate.
Fluoxetine toxicity in a newborn may be caused by the parent compound, fluoxetine, and side effects may be caused by the parent compound.
Case Report
Highly CitedPharmacokinetics of Fluoxetine in Rhesus Macaques following Multiple Routes of Administration
Fluoxetine maintains human clinical range serum concentrations in rhesus macaques when administered orally, with norfluoxetine being the greater drug concentration in the blood stream.
Non-RCT
Animal StudyFluoxetine: A Serotonin‐specific, Second‐generation Antidepressant
Fluoxetine is a serotonin-specific, second-generation antidepressant with comparable efficacy to tricyclic agents and low side effects.
Highly CitedRelevance of Half-Life in Drug Design.
Drug half-life is crucial for dosing regimen and peak-to-trough ratio, and optimizing it through structural modification can improve efficacy, safety, and patient compliance.
Highly CitedThe Practical Importance of Half-Life in Psychopharmacology.
Half-life is crucial in psychopharmacology, influencing dosing frequency, adverse effects risk, and drug duration, affecting prescription decisions.
Psychotropic Drugs With Long Half-Lives: Implications for Drug Discontinuation, Occasional Missed Doses, Dosing Interval, and Pregnancy Planning.
Psychotropic drugs with long half-lives have a small risk of withdrawal, but may require pregnancy planning due to occasional missed doses, once-weekly dosing, and the need for rapid washout.
Cost-effectiveness and cost-utility of cognitive therapy, rational emotive behavioral therapy, and fluoxetine (Prozac) in treating depression: a randomized clinical trial.
Cognitive therapy and rational emotive behavioral therapy are more cost-effective and have better cost-utility than pharmacotherapy for treating depression.
RCTHighly CitedContext-sensitive half-time in multicompartment pharmacokinetic models for intravenous anesthetic drugs.
Context-sensitive half-times are a more useful parameter for describing intravenous anesthetic drug disposition during relevant infusion durations, rather than elimination half-life.
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