Fluoxetine

SSRI·Psychiatry - Antidepressants

Major Depressive Disorder, OCD, Bulimia Nervosa, PMDD

PBSSSRIProzac, Lovan, Zactin20 mg tabletS4+1

Max Dose

80 mg/day

Half-life

4-6 DAYS

CYP Inhibitor

POTENT

Activation

COMMON

Rapid Summary

Overview

The original SSRI (Prozac). Highly activating and boasts a phenomenally long half-life. Excellent for non-compliant patients, but a nightmare for drug interactions.

Maximum Dose

Max 80 mg/day (e.g., OCD/Bulimia). Normal depression max is 20-40 mg/day.

Clinical Focus

Completely shuts down CYP2D6. Active metabolites stay in the blood for 5 WEEKS after stopping. You cannot safely start a new drug immediately after ceasing Fluoxetine.

Bottom Line

Fluoxetine is the longest-acting SSRI ideal when discontinuation syndrome is a concern, but has a very long washout period (5 weeks) before MAOI initiation and causes more activation/insomnia than other SSRIs.

Formulation & Access

Brand Names

Prozac, Lovan, Zactin

Oral Routes

Capsules/Tablets (20 mg). Dispersible tablets (20 mg).

Prescribing & PBS

Unrestricted General Benefit (S4).

Indications & Use

Primary

PBSTGA

Major Depressive Disorder, OCD, Bulimia Nervosa, PMDD.

Clinical Place

The first-line SSRI for children and adolescents (best evidence base). Excellent for adults with high fatigue/hypersomnia who need an 'activating' kick.

Quick reference

Class & Role

SSRI — The original SSRI (Prozac).

Route / Formulation

Capsules/Tablets (20 mg). Dispersible tablets (20 mg). (Prozac, Lovan, Zactin)

Usual Dose & Max

PO 20 mg OD (strictly in the morning to prevent insomnia). Max 80 mg/day.

Key Indication Doses

Depression / Anxiety: PO 20 mg OD (strictly in the morning to prevent insomnia). Max 80 mg/day. Bulimia Nervosa: PO 60 mg OD (Requires high doses for impulse control). Washout Period: Must wait exactly 5 WEEKS after stopping Fluoxetine before starting an MAOI (Phenelzine) or severe fatal Serotonin Syndrome will occur.

Best Uses

Avoid / Cautions

Concurrent MAOI use, Pimozide use. Pregnancy Category C.

Key Risks

Neurological: Insomnia, severe initial anxiety/agitation, tremor. CRITICAL — Serotonin Syndrome. Gastrointestinal: Nausea, diarrhea, anorexia (weight loss is common initially). Endocrine/GU: Sexual dysfunction. Metabolic: Hyponatremia (SIADH).

Key Interactions

Potent irreversible inhibitor of CYP2D6. Will completely block Codeine/Tramadol from working. Will massively spike levels of Risperidone, Metoprolol, and TCAs into the toxic range. NSAIDs and Aspirin (Doubles risk of upper GI bleeds).

Monitoring

Warn the patient about intense anxiety/jitteriness in the first week. Take in the morning only. Check U&E (sodium) at 2-4 weeks in the elderly.

Clinical Pearl

Because Norfluoxetine lasts for 16 days in the blood, if a patient forgets their pill for 3 days, their blood levels barely drop. They suffer ZERO withdrawal or 'brain zaps'. It is the best drug for chaotic, non-compliant patients.

Access

Prozac, Lovan, Zactin20 mg tablet

Brand: Prozac, Lovan, Zactin
Formulation: Capsules/Tablets (20 mg)