Symptomatic orthostatic hypotension after antiemetic therapy with prochlorperazine: A case report

INTRODUCTION

Orthostatic hypotension (OH) is defined as a sustained reduction in systolic blood pressure of at least 20 mmHg or diastolic blood pressure of at least 10 mmHg within 3 min of standing or head-up tilt to at least 60°.^[1] This condition affects 5–30% of the general population and is associated with increased risk of falls, syncope, cognitive impairment, and cardiovascular events.^[1] Prochlorperazine is a first-generation antipsychotic belonging to the phenothiazine class, primarily used as an antiemetic agent. It functions by blocking dopamine D2 receptors in the chemoreceptor trigger zone and vomiting center.^[2] While effective for managing nausea and vomiting, prochlorperazine shares the adverse effect profile common to antipsychotic medications, including cardiovascular complications such as orthostatic hypotension.^[3]

Antipsychotic-induced orthostatic hypotension results from α1-adrenergic receptor blockade, leading to peripheral vasodilation and impaired vasoconstriction on postural changes.^[4] The incidence and severity of this adverse effect vary among different antipsychotic agents, with phenothiazines demonstrating notable α1-adrenergic antagonism.^[4] While orthostatic hypotension is well-documented with antipsychotics used for psychiatric indications in elderly or medically complex populations, case reports documenting this adverse effect in young, healthy individuals receiving prochlorperazine for antiemetic purposes are notably sparse in the published literature. This case report presents a clinically significant episode of orthostatic hypotension temporally associated with prochlorperazine initiation in a young adult without traditional risk factors, emphasizing the need for vigilant cardiovascular monitoring across all patient populations.

CASE REPORT

A 38-year-old male presented to the outpatient clinic 14 days after initiating prochlorperazine therapy, reporting a 9-day history of progressive dizziness and presyncope. Two weeks before presentation, he had sought care at an urgent care facility for persistent nausea and occasional vomiting lasting 3–4 days, for which no specific etiology was identified. He was prescribed prochlorperazine 10 mg orally 3 times daily as needed for nausea control and initiated therapy immediately on leaving the facility. During the first 4 days of treatment, he took the medication 2–3 times daily (total daily dose 20–30 mg) with effective nausea control, maintained adequate oral fluid intake of approximately two liters daily, and experienced no adverse effects. On the 5^th day after medication initiation, he experienced his first episode of dizziness on standing from a seated position in the morning, lasting approximately 3 minutes before gradually resolving. Additional episodes occurred throughout that day with position changes. Over the subsequent 9 days, orthostatic symptoms progressively worsened in both frequency and severity, with near-syncope episodes characterized by sensations of impending loss of consciousness, lightheadedness, and visual blurring that necessitated sitting or lying down to prevent falls. The patient continued taking prochlorperazine at similar dosing during this period due to persistent nausea. No actual syncope occurred, but the increasing severity and frequency of symptoms prompted him to seek medical evaluation.

The patient’s medical history was unremarkable, with no chronic medication use and no prior diagnosis of hypertension, cardiac arrhythmias, myocardial infarction, cerebrovascular disease, or diabetes mellitus. He was not taking any prescription medications, over-the-counter medications, herbal supplements, or dietary supplements at the time of presentation. Family history was negative for sudden cardiac death or inherited cardiac conditions. Social history revealed nonsmoking status with occasional alcohol consumption of one to two drinks weekly, and he denied any recent illicit drug use. He worked in an office environment with no unusual heat exposure or changes in physical activity levels during the symptomatic period, and he reported maintaining his usual diet and fluid intake throughout.

A thorough systemic evaluation, including respiratory, cardiovascular, and neurological examination, was unremarkable, and no signs of autonomic disturbances were noted either. Electrocardiogram and other laboratory investigations, such as complete blood count, liver and kidney function tests, serum electrolytes, and arterial blood gas, were all found to be within normal range.

Orthostatic vital signs were obtained following a standardized protocol. After remaining supine for 10 min with a baseline blood pressure of 138/84 mmHg and a heart rate of 74 beats/ min, the patient stood upright, and measurements were repeated after exactly 3 min of standing. Standing blood pressure measured 104/62 mmHg, representing a 34 mmHg systolic and 22 mmHg diastolic decline from baseline, while heart rate increased to 94 beats/min, a 20 beat/min increase. The patient reported moderate dizziness and lightheadedness during measurement, symptoms identical to his chief complaint. No syncope occurred during testing, though he required reassurance and close monitoring throughout the procedure.

Given the clear temporal relationship between prochlorperazine initiation and symptom onset 5 days later, progressive worsening over 9 days, absence of alternative etiologies on comprehensive workup, and presence of documented orthostatic hypotension on examination, prochlorperazine-induced orthostatic hypotension was diagnosed. The Naranjo Adverse Drug Reaction Probability Scale was applied systematically, yielding a score of 7.^[5] Rechallenge was not performed as it was deemed ethically inappropriate given symptom severity and availability of alternative antiemetic agents. Alternative diagnoses, including volume depletion, viral illness, primary autonomic dysfunction, cardiac causes, and endocrine disorders, were systematically excluded based on history, physical examination, and laboratory findings.

Prochlorperazine was immediately discontinued, and the patient received comprehensive counseling on nonpharmacological management strategies including increased fluid intake to 2.5–3 L daily, adequate salt intake of 8–10 g daily, gradual postural changes, lower extremity muscle tensing and leg crossing when standing, consideration of waist-high compression stockings (30–40 mmHg) if symptoms persisted, avoidance of prolonged standing, head-of-bed elevation by 4–6 inches, and avoidance of large meals and alcohol. The patient was counseled to avoid prochlorperazine and other phenothiazine derivatives permanently, and alternative antiemetic options were discussed, including ondansetron, metoclopramide (with caution), and non-pharmacological approaches. At 48-h telephone follow-up, the patient reported significant improvement with only one brief episode of mild dizziness lasting <1 min, adherence to fluid intake recommendations and postural precautions, and complete resolution of nausea. Two-week follow-up demonstrated complete symptom resolution with no dizziness, presyncope, or orthostatic symptoms over the preceding 12 days. Repeat orthostatic vital signs showed blood pressure of 126/76 mmHg supine, decreasing to 118/72 mmHg after standing (8 mmHg systolic drop) with heart rate increasing from 70 to 78 beats/min, findings within normal physiological parameters confirming resolution of drug-induced orthostatic hypotension. Three-month follow-up revealed sustained complete resolution of symptoms, blood pressure of 124/78 mmHg, no recurrence of nausea, maintenance of healthy lifestyle habits, and no medication use, with reinforcement of education regarding permanent avoidance of phenothiazines.

DISCUSSION

This case demonstrates clinically significant prochlorperazine-induced orthostatic hypotension in a young, healthy patient without traditional risk factors. Comprehensive laboratory evaluation confirmed metabolic health (HbA1c 5.4%), normal renal function, and no electrolyte disturbances, establishing prochlorperazine as the sole causative agent. Phenothiazines cause orthostatic hypotension through α1-adrenergic receptor antagonism, impairing compensatory vasoconstriction during postural changes.^[4] When standing normally triggers baroreceptor-mediated sympathetic activation, α1-receptor blockade prevents peripheral vasoconstriction, leading to venous pooling and reduced cardiac preload. This occurrence in a healthy 38-year-old highlights prochlorperazine’s potent α1-blocking properties, with the drug’s pharmacological effects alone overwhelming normal compensatory mechanisms. Unlike elderly patients with age-related autonomic dysfunction or patients with autonomic neuropathy from diabetes, this patient had demonstrably normal cardiovascular reflexes before medication initiation, as confirmed by normal baseline laboratories and absence of prior symptoms, suggesting the drug’s pharmacological effects alone overwhelmed normal compensatory mechanisms. Complete symptom resolution within 2 weeks of discontinuation supports this conclusion.

The delayed symptom onset on day 5 likely reflects pharmacokinetic accumulation, as prochlorperazine’s 6–8 h half-life achieves steady-state concentrations after 3–5 days of regular dosing, with progressive receptor occupancy eventually exceeding the threshold for maintaining adequate vasoconstriction. The absence of concomitant medications strengthens causality by eliminating polypharmacy and drug–drug interactions as contributing factors. Similar cases with olanzapine and risperidone reported in the literature underscore the importance of recognizing orthostatic hypotension as a class effect across all antipsychotic medications, regardless of indication or patient demographics.^[6,7]

This case emphasizes several clinical considerations. Orthostatic hypotension should be recognized as a potential prochlorperazine adverse effect even in young, healthy patients, and baseline orthostatic vital signs should be considered for all patients initiating antipsychotic therapy. Patients require counseling about orthostatic symptoms, preventive measures including slow position changes and adequate hydration, and recognition of presyncope warning signs. When prescribing antiemetics, clinicians should consider varying risk profiles: ondansetron offers lower cardiovascular risk, metoclopramide represents moderate risk, while prochlorperazine and chlorpromazine carry higher cardiovascular risk due to significant α1-adrenergic antagonism. Management with medication discontinuation and conservative measures (hydration, salt intake, gradual position changes, compression stockings) resulted in complete symptom resolution, demonstrating the effectiveness of this approach for drug-induced orthostatic hypotension.^[1]

CONCLUSION

This case underscores that prochlorperazine-induced orthostatic hypotension can occur in young, healthy individuals without traditional risk factors. Clinicians should maintain heightened awareness of this adverse effect when prescribing antipsychotic medications for any indication, including antiemetic therapy. Baseline orthostatic vital sign assessment, patient education regarding potential symptoms, and consideration of alternative antiemetic agents may help mitigate this cardiovascular complication and improve patient safety across all demographics.