From the FDA Drug Label
Among 633 adult patients who overdosed on fluoxetine hydrochloride alone, 34 resulted in a fatal outcome, 378 completely recovered, and 15 patients experienced sequelae after overdosage, including abnormal accommodation, abnormal gait, confusion, unresponsiveness, nervousness, pulmonary dysfunction, vertigo, tremor, elevated blood pressure, impotence, movement disorder, and hypomania The most common signs and symptoms associated with non–fatal overdosage were seizures, somnolence, nausea, tachycardia, and vomiting. Other important adverse events reported with fluoxetine overdose (single or multiple drugs) include coma, delirium, ECG abnormalities (such as QT interval prolongation and ventricular tachycardia, including torsades de pointes–type arrhythmias), hypotension, mania, neuroleptic malignant syndrome–like events, pyrexia, stupor, and syncope Signs and symptoms of hyponatremia include headache, difficulty concentrating, memory impairment, confusion, weakness, and unsteadiness, which may lead to falls More severe and/or acute cases have been associated with hallucination, syncope, seizure, coma, respiratory arrest, and death.
Syncope and orthostatic hypotension can be associated with fluoxetine use, as evidenced by reports of syncope in the context of overdose and hyponatremia, which may lead to falls and can be a sign of orthostatic hypotension. However, the exact relationship between fluoxetine and orthostatic hypotension is not explicitly stated in the provided drug labels. 1 1
From the Research
Fluoxetine (Prozac) is not typically associated with causing syncope or orthostatic hypotension, and in some cases, it may even be used to treat these conditions. When considering the potential for fluoxetine to cause syncope or orthostatic hypotension, it's essential to weigh the evidence. While some studies suggest that fluoxetine may have a role in treating orthostatic hypotension 2 or preventing vasovagally mediated syncope 3, other factors such as patient-specific conditions, dosage, and concomitant medications must be considered. The most recent and highest quality study on the treatment of primary orthostatic hypotension suggests that non-pharmacological strategies are the primary treatment, and if these fail, pharmacotherapy can help ameliorate symptoms 4. Key points to consider include:
- Fluoxetine's potential effects on blood pressure regulation, particularly in patients with pre-existing cardiovascular conditions or those taking other medications that affect blood pressure.
- The importance of gradual dose increases and monitoring for orthostatic hypotension or syncope, especially in elderly patients or those with a history of cardiovascular disease.
- The need for individualized treatment approaches, taking into account patient-specific factors such as tolerability, adverse effects, and drug-drug and drug-disease interactions 4. In clinical practice, if a patient experiences dizziness or syncope while taking fluoxetine, it is crucial to consult a healthcare provider to assess the situation and adjust the treatment plan as necessary, rather than abruptly stopping the medication.