A 2022 study which examined the health insurance claims of over 2 million Americans who began taking oxycodone while using SSRIs between 2000 and 2020, found that patients taking paroxetine or fluoxetine had a 23% higher risk of overdosing on oxycodone than those using other SSRIs.There is also the potential for interaction with highly protein-bound drugs due to the potential for fluoxetine to displace said drugs from the plasma or vice versa hence increasing serum concentrations of either fluoxetine or the offending agent. Pharmacology
Pharmacodynamics
Fluoxetine is a selective serotonin reuptake inhibitor (SSRI) and does not appreciably inhibit norepinephrine and dopamine reuptake at therapeutic doses. It does, however, delay the reuptake of serotonin, resulting in serotonin persisting longer when it is released. Large doses in rats have been shown to induce a significant increase in synaptic norepinephrine and dopamine. Thus, dopamine and norepinephrine may contribute to the antidepressant action of fluoxetine in humans at supratherapeutic doses (60–80 mg). This effect may be mediated by 5HT2C receptors, which are inhibited by higher concentrations of fluoxetine.Fluoxetine increases the concentration of circulating allopregnanolone, a potent GABAA receptor positive allosteric modulator, in the brain. Norfluoxetine, a primary active metabolite of fluoxetine, produces a similar effect on allopregnanolone levels in the brains of mice. Additionally, both fluoxetine and norfluoxetine are such modulators themselves, actions which may be clinically-relevant.In addition, fluoxetine has been found to act as an agonist of the σ1-receptor, with a potency greater than that of citalopram but less than that of fluvoxamine.
Signs and symptoms
Signs and symptoms of familial dysautonomia usually commence during infancy and worsen with age, and may include: gastrointestinal dysmotility (including erratic gastric emptying, gastroesophageal reflux, abnormal esophageal peristalsis, oropharyngeal incoordination), dysphagia (as poor suckling in infancy) and frequent choking/gagging, recurrent vomiting, poor weight gain/growth, delayed development (especially walking) and puberty (especially in girls), recurrent aspiration pneumonia (due to inhalation of food or vomitus) with possible secondary chronic lung disease, absence of overflow tears during crying, corneal ulcers, red skin blotches and excessive sweating (often during eating or excitement), breath-holding spells, slurred speech/nasal voice, tongue ulcers (from accidental self-injuries), hyporeflexia (variable absence of deep tendon reflexes), hypotonia, enuresis, arrhythmias, hypertension (including episodic hypertension in response to emotional stress or visceral pain), hypotension (including orthostatic hypertension with compensatory tachycardia (invariably present)), impaired (but not absent) temperature and pain perception (leading to frequent accidental injury), impaired proprioception, a smooth glossy tongue, scoliosis (with possibly secondary restrictive lung disease), abnormal gait, short stature, chronic renal failure (common), visual impairment, variable cognitive ability, characteristic facial features that develop with time, impaired vibration perception, lack of fungiform papilla of the tongue, and impaired taste perception (especially for sweetness). Autonomic crises - In children with FD, recurrent episodes of vomiting may occur. Such episodes may be triggered by physical (e.g. infection) or emotional stress, may occur every 15–20 minutes for over 24 hours, and may be accompanied with: significant hypertension, drenching sweat, breathing issues, fever, tachycardia, aspiration pneumonia, skin blotches, drooling, and negative personality change.