Effect of midodrine on chlorpromazine-induced orthostatic hypotension in rabbits: comparison with amezinium, etilefrine and droxidopa

Midodrine-Induced Nightmares in the Treatment of Orthostatic Hypotension: A Case Report

Background Midodrine was the first medication approved by the Food and Drug Administration (FDA) for the treatment of orthostatic hypotension. Pharmacologically, midodrine is a peripheral selective alpha-1-adrenergic agonist that can improve standing, sitting, and supine systolic blood pressure. Common side effects include bradycardia, supine hypertension, and paresthesia. A novel side effect of midodrine-induced nightmares has been reported in our patient. To our knowledge, this is the first reported case of midodrine-induced nightmares. Objective To investigate and report a clinically significant and unique drug adverse event of midodrine in the treatment of orthostatic hypotension. Case Presentation This report describes a case of persistent nightmares associated with midodrine use in an 83-year-old male who experienced frequent syncope episodes treated with midodrine for orthostatic hypotension (OH). After the initiation of midodrine, the patient complained of increased nightmares, which quickly led to his refusal of the medication, despite the initial improvements in his blood pressure. The timing of administration included an evening dose at 21:00. This novel adverse event of midodrine-induced nightmares will be highlighted and explored in this case report. Conclusion This case demonstrated a unique adverse event of nightmares caused by midodrine. It is hypothesized that autonomic dysfunction plays a role and further investigations should be conducted to confirm this theory. We hope that our case report highlights the importance of careful consideration when prescribing midodrine in older people with orthostatic hypotension.

Anti-hypotensive effect of “Yahom Navakot” in rats with orthostatic hypotension

Background and aim

Yahom Navakot (YN), is a Thai traditional medicine, consisting of 54 plants, for treating fainting and dizziness. Thus, YN might relieve orthostatic hypotension (OH) symptoms, but its therapeutic action is unclear. Therefore, this study evaluated YN in OH rats, using a head-up tilt test (HUT).

Experimental procedure

Rats were anesthetized, and OH induced via a 90^oHUT, before and after administering vehicle, a YN powder suspension (10, 100 mg/kg), a YN aqueous extract (100 mg/kg), and midodrine (5 mg/kg). The systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial blood pressure (MAP), pulse pressure (PP) and heart rate (HR) were determined via the carotid artery. Plasma noradrenaline (NA) was evaluated. YN-induced vasoconstriction of isolated rat aorta rings was determined using organ bath technique.

Results and conclusion

Baseline BP increased with the 100 mg/kg YN powder suspension, the YN aqueous extract or midodrine, while HR decreased, compared with vehicle and control. 90^oHUT rapidly reduced SBP, DPB and MAP, but increased HR, for control and vehicle-treated groups, but BP was steady with the 100 mg/kg YN powder suspension, the YN aqueous extract or midodrine. The 90^oHUT-increase in HR was most pronounced with the 100 mg/kg YN powder suspension (the traditional formulation). This accords with increased plasma NA. YN also induced vasoconstriction in rat aorta via α₁-receptor activation. Thus, the anti-hypotensive action of YN involved a stimulating effect on the heart and blood vessels via sympathetic activation. The results support the traditional use of YN and demonstrated the effectiveness of YN for OH prevention.

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Yahom Navakot is an effective treatment for orthostatic hypotension.

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Yahom Navakot possesses chronotropic effect and vasoconstrictor action.

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Yahom Navakot increases plasma noradrenaline leading to the increase in blood pressure.

Droxidopa for the treatment of neurogenic orthostatic hypotension in neurodegenerative diseases

INTRODUCTION

L-threo-3,4-dihydroxyphenylserine (droxidopa), a pro-drug metabolized to norepinephrine in nerve endings and other tissues, has been commercially available in Japan since 1989 for treating orthostatic hypotension symptoms in Parkinson's disease (PD) patients with a Hoehn & Yahr stage III rating, as well as patients with Multiple System Atrophy (MSA), familial amyloid polyneuropathy, and hemodialysis. Recently, the FDA has approved its use in symptomatic neurogenic orthostatic hypotension (NOH). Areas covered: The authors review the effects of droxidopa in NOH with a focus on the neurodegenerative diseases PD, MSA, and pure autonomic failure (PAF). Expert opinion: A few small and short placebo-controlled clinical trials in NOH showed significant reductions in the manometric drop in blood pressure (BP) after posture changes or meals. Larger Phase III studies showed conflicting results, with two out of four trials meeting their primary outcome and thus suggesting a positive yet short-lasting effect of the drug on OH Questionnaire composite score, light-headedness/dizziness score, and standing BP during the first two treatment-weeks. Results appear essentially similar in PD, MSA, and PAF. The FDA granted droxidopa approval in the frame of an 'accelerated approval program' provided further studies are conducted to assess its long-term effects on OH symptoms.

Management of common adverse effects of antipsychotic medications

The benefits of antipsychotic medications are sometimes obscured by their adverse effects. These effects range from relatively minor tolerability issues (e.g., mild sedation or dry mouth) to very unpleasant (e.g., constipation, akathisia, sexual dysfunction) to painful (e.g., acute dystonias) to disfiguring (e.g., weight gain, tardive dyskinesia) to life-threatening (e.g., myocarditis, agranulocytosis). Importantly, adverse effect profiles are specific to each antipsychotic medication and do not neatly fit into first- and second-generation classifications. This paper reviews management strategies for the most frequent side effects and identifies common principles intended to optimize net antipsychotic benefits. Only use antipsychotics if the indication is clear; only continue antipsychotics if a benefit is discernible. If an antipsychotic is providing substantial benefit, and the adverse effect is not life-threatening, then the first management choice is to lower the dose or adjust the dosing schedule. The next option is to change the antipsychotic; this is often reasonable unless the risk of relapse is high. In some instances, behavioral interventions can be tried. Finally, concomitant medications, though generally not desirable, are necessary in many instances and can provide considerable relief. Among concomitant medication strategies, anticholinergic medications for dystonias and parkinsonism are often effective; beta-blockers and anticholinergic medications are useful for akathisia; and metformin may lead to slight to moderate weight loss. Anticholinergic drops applied sublingually reduce sialorrhea. Usual medications are effective for constipation or dyslipidemias. The clinical utility of recently approved treatments for tardive dyskinesia, valbenazine and deutetrabenazine, is unclear.

Orthostatic hypotension in the anesthetized rabbit in the sitting position exceeds cerebral autoregulation

BACKGROUND

Orthostatic hypotension and cerebral autoregulation have been extensively studied in the rabbit. However, these physiologic responses have not been previously studied utilizing a rabbit in the sitting position under anesthesia.

METHODS

This unusual position was obtained as the preferred orientation based on geometry requirements of associated equipment for a study of osteoarthritis of the knee. Rabbits for this experiment did not survive and an additional experimental condition was developed to elucidate the mechanism and cause of death. The carotid artery pressure was measured under general anesthesia with incremental tilt testing to achieve the sitting position.

RESULTS

Under this condition, rabbits developed orthostatic hypotension and did not survive.

CONCLUSIONS

According to previous studies of orthostatic hypotension and limits of cerebral autoregulation, it is concluded that orthostatic hypotension in the anesthetized rabbit in the sitting position exceeds cerebral autoregulation.