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Fluoxetine; Uses, Dosage, Side Effects, Interactions, Pregnancy

Fluoxetine hydrochloride is the first agent of the class of antidepressants known as selective serotonin-reuptake inhibitors (SSRIs). Despite distinct structural differences between compounds in this class, SSRIs possess similar pharmacological activity. As with other antidepressant agents, several weeks of therapy may be required before a clinical effect is seen. SSRIs are potent inhibitors of neuronal serotonin reuptake. They have little to no effect on norepinephrine or dopamine reuptake and do not antagonize & alpha; – or & beta; -adrenergic, dopamine D 2 or histamine H 1 receptors. During acute use, SSRIs block serotonin reuptake and increase serotonin stimulation of somatodendritic 5-HT 1A and terminal autoreceptors. Chronic use leads to desensitization of somatodendritic 5-HT 1A and terminal autoreceptors. The overall clinical effect of increased mood and decreased anxiety is thought to be due to adaptive changes in neuronal function that leads to enhanced serotonergic neurotransmission. Side effects include dry mouth, nausea, dizziness, drowsiness, sexual dysfunction and headache. Side effects generally occur within the first two weeks of therapy and are usually less severe and frequent than those observed with tricyclic antidepressants. Fluoxetine may be used to treat major depressive disorder (MDD), moderate to severe bulimia nervosa, obsessive-compulsive disorder (OCD), premenstrual dysphoric disorder (PMDD), panic disorder with or without agoraphobia, and in combination with olanzapine for treatment-resistant or bipolar I depression. Fluoxetine is the most anorexic and stimulating SSRI.

Fluoxetine is the first agent of the class of antidepressants known as selective serotonin-reuptake inhibitors (SSRIs & an antidepressant of the selective serotonin reuptake inhibitor (SSRI) class. It is used for the treatment of the major depressive disorder, obsessive-compulsive disorder (OCD), bulimia nervosa, panic disorder, and premenstrual dysphoric disorder.

Mechanism of action of Fluoxetine

Metabolized to norfluoxetine, fluoxetine is a selective serotonin-reuptake inhibitor (SSRI), it blocks the reuptake of serotonin at the serotonin reuptake pump of the neuronal membrane, enhancing the actions of serotonin on 5HT_1A autoreceptors. SSRIs bind with significantly less affinity to histamine, acetylcholine, and norepinephrine receptors than tricyclic antidepressant drugs. According to the amines hypothesis, a functional decrease in the activity of amines, such as serotonin and norepinephrine, would result in depression; a functional increase of the activity of these amines would result in mood elevation. Fluoxetine’s effects are thought to be associated with the inhibition of 5HT receptor, which leads to an increase of serotonin level. Antagonism of muscarinic, histaminergic, and α1–adrenergic receptors has been hypothesized to be associated with various anticholinergic, sedative, and cardiovascular effects of classical tricyclic antidepressant (TCA) drugs. Fluoxetine binds to these and other membrane receptors from brain tissue much less potently in vitro than do the tricyclic drugs.

Indications of Fluoxetine

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Labeled indication include: major depressive disorder (MDD), moderate to severe bulimia nervosa, obsessive-compulsive disorder (OCD), premenstrual dysphoric disorder (PMDD), panic disorder with or without agoraphobia, and combination treatment with olanzapine for treatment-resistant or bipolar I depression. Unlabeled indications include selective mutism, mild dementia-associated agitation in nonpsychotic patients, post-traumatic stress disorder (PTSD), social anxiety disorder, chronic neuropathic pain, fibromyalgia, and Raynaud’s phenomenon.

Contra Indications of Fluoxetine

Diabetes
Syndrome of Inappropriate Antidiuretic Hormone Secretion
low amount of magnesium in the blood
low amount of sodium in the blood
low amount of potassium in the blood
increased risk of bleeding
Behaving with Excessive Cheerfulness and Activity
Mild Degree of Mania
Manic-Depression
Having Thoughts of Suicide
Serotonin syndrome – adverse drug interaction
Closed-angle glaucoma
heart attack within the last 30 days
Very Rapid Heartbeat – Torsades de Pointes
Slow Heartbeat
prolonged QT interval on EKG
Suddenly serious symptoms of heart failure
Abnormal EKG with QT changes from Birth
Hardening of the Liver
Liver problems
Bleeding from Stomach
Esophagus or Duodenum
seizures

Dosages of Fluoxetine

Strengths: 90 mg; 10 mg; 20 mg; 40 mg; 20 mg/5 mL; 15 mg; 60 mg

Depression

Immediate-release oral formulations

Initial dose: 20 mg orally once a day in the morning, increased after several weeks if sufficient clinical improvement is not observed

Maintenance dose: 20 to 60 mg orally per day
Maximum dose: 80 mg orally per day

Delayed release oral capsules

Initial dose: 90 mg orally once a week, commenced 7 days after the last daily dose of immediate-release fluoxetine 20 mg formulations.

Obsessive Compulsive Disorder

Immediate-release oral formulations

Initial dose: 20 mg orally once a day in the morning, increased after several weeks if sufficient clinical improvement is not observed.
Maintenance dose: 20 to 60 mg orally per day
Maximum dose: 80 mg orally per day

Panic Disorder

Immediate-release oral formulations

Initial dose: 10 mg orally once a day, increased after one week to 20 mg orally once a day
Maintenance dose: 20 to 60 mg orally per day
Maximum dose: 60 mg orally per day

Premenstrual Dysphoric Disorder

Immediate-release oral formulations
Initial dose

Continuous regimen: 20 mg orally once a day on every day of the menstrual cycle
Cyclic regimen: 20 mg orally once a day starting 14 days prior to the anticipated start of menstruation through to the first full day of menses, and repeated with each new cycle
Maintenance dose: 20 to 60 mg per day for either the continuous or intermittent regimens
Maximum dose: 80 mg orally per day

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Pediatric Dose for Depression

Immediate-release oral formulations
8 to 18 years

Initial dose: 10 to 20 mg orally once a day; the 10 mg daily dose may be increased after one week to 20 mg orally once a day

Pediatric Dose for Obsessive Compulsive Disorder

Immediate-release oral formulations
7 to 17 years

Adolescents and higher weight children
Initial dose: 10 mg orally once a day, increased to 20 mg orally once a day after 2 weeks
Maintenance dose: 20 to 60 mg orally per day
Maximum dose: 60 mg orally per day

Side Effects of Fluoxetine

The most common

clumsiness or unsteadiness
dizziness
drowsiness
dry mouth
false sense of well-being
increased watering of mouth
lightheadedness
constipation;
vision changes;
breast swelling (in men or women); or
decreased sex drive, impotence, or difficulty having an orgasm.
blurred vision, tunnel vision, eye pain or swelling, or seeing halos around lights;
restless muscle movements in your eyes, tongue, jaw, or neck;
a light-headed feeling, like you, might pass out;

Common

Drowsiness and lightheadedness the day after taking the medicine.
Confusion.
Numbed emotions.
Visual disturbances such as blurred vision or double vision.
Shaky movements and unsteady walk (ataxia).
Loss of memory (amnesia).
Muscle weakness.
Dizziness.
A headache.
Skin rashes.
Disturbances of the gut such as diarrhea, c onstipation, nausea, vomiting or abdominal pain.
Difficulty in passing urine (urinary retention).
Changes in sex drive.
Low blood pressure (hypotension).
Blood disorders.
Jaundice.
Unexpected aggression, restlessness or irritability (tell your doctor if you experience this).
Nightmares or hallucinations (tell your doctor if you experience this).

Serious

agitation
anxiety
behavioral changes, including aggressiveness, angry outbursts, bizarre behavior, or decreased inhibitions
confusion
increased trouble sleeping
memory problems
muscle spasms
shortness of breath
signs of depression (e.g., poor concentration, changes in weight, changes in sleep, decreased interest in activities, thoughts of suicide)
sleepwalking

Drug Interactions of Fluoxetine

Fluoxetine may interact with following drugs, supplements & may change the efficacy of drugs

amlodipine
general anesthetics
antihistamines (e.g., cetirizine, doxylamine, diphenhydramine, hydroxyzine, loratadine)
antipsychotics (e.g., chlorpromazine, clozapine, haloperidol, olanzapine, quetiapine, risperidone)
aripiprazole
baclofen
barbiturates (e.g., butalbital, pentobarbital, phenobarbital)
benzodiazepines (e.g., alprazolam, diazepam, lorazepam)
bupropion
celecoxib
cilostazol
clopidogrel
cyclosporine
diabetes medications (e.g., chlorpropamide, metformin, nateglinide, rosiglitazone)
diltiazem
estrogens (e.g., conjugated estrogen, )
glucosamine
heparin
low molecular weight heparins
mirtazapine
monoamine oxidase inhibitors (MAOIs; e.g. rasagiline, selegiline, )
multivitamins
muscle relaxants
nifedipine
non-steroidal anti-inflammatory medications (NSAIDs; e.g., diclofenac, ibuprofen, naproxen)
omega-3 fatty acids
pentoxifylline
propranolol
quinolone antibiotics (e.g., ciprofloxacin, norfloxacin, ofloxacin)
rasagiline
seizure medications ( phenobarbital, phenytoin, valproic acid, )
selective serotonin reuptake inhibitors (SSRIs; e.g., citalopram, duloxetine, fluoxetine, paroxetine, sertraline)
serotonin antagonists (anti-emetic medications; e.g., granisetron, ondansetron)
tapentadol
theophyllines (e.g., aminophylline, oxtriphylline, theophylline)
thiazide diuretics (water pills; e.g., hydrochlorothiazide, )
thyroid replacements (e.g., desiccated thyroid, levothyroxine)
tizanidine
tramadol
tricyclic antidepressants (e.g., desipramine, nortriptyline)
triptans (e.g., sumatriptan, rizatriptan)

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Pregnancy & Lactation of Fluoxetine

FDA Pregnancy Category C

Pregnancy

If you are pregnant or breastfeeding, think you may be pregnant or are planning to have a baby, ask your doctor, pharmacist or nurse for advice before taking this medicine. When taken during pregnancy, particularly in the last 3 months of pregnancy, medicines like Fluoxetine may increase the risk of a serious condition in babies, called persistent pulmonary hypertension of the newborn (PPHN), making the baby breathe faster and appear bluish. These symptoms usually begin during the first 24 hours after the baby is born.

Lactation

Breastfeeding is not recommended whilst taking fluoxetine. Fluoxetine has been shown to reduce the quality of sperm in animal studies. Theoretically, this could affect fertility, but the impact on human fertility has not been observed as yet.