Dizziness and Vertigo _________________________________________________________________________
VESTIBULAR SUPPRESSANT MEDICATIONS
Medication
Dosage and Route
Antihistamine Agents Diphenhydramine
50 mg PO twice daily 10–50 mg IM or IV
Meclizine
25–50 mg PO three to four times per day 12.5–50 mg PO every four to six hours 50 mg RS four times per day 10–50 mg IM or IV 0.5–2 mg PO two to three times per day 2–5 mg PO three to four times per day 0.25–1 mg PO two to three times per day 10–20 mg PO every four to six hours 10–20 mg IM or IV 10–20 mg PO every four to six hours 25 mg RS every six hours 5–10 mg IM or IV 10–20 mg PO every six to eight hours
Promethazine
Benzodiazepines Lorazepam
Diazepam
Clonazepam
Antiemetic Agents Metoclopramide
Prochlorperazine
Domperidone Ondansetron
8 mg PO every 6 to 12 hours 4 mg SL, IM, or IV
Anti-Motion Sickness Scopolamine
1 TD patch (1.5 mg) every three days IM = intramuscular; IV = intravenous; PO = oral; RS = rectal suppository; SL = sublingual; TD = transdermal. Source: [15; 21; 120; 124; 128]
Table 2
Scopolamine is a belladonna alkaloid that blocks CNS neuro- transmission of acetylcholine and is one of the most effective agents for preventing motion sickness. Scopolamine is also effective for vestibular-mediated nausea/vomiting and is bet- ter tolerated as a transdermal patch than when taken orally. Common side effects are sedation, constipation, dry mouth, and urinary retention [115; 125]. Dopamine antagonists (e.g., metoclopramide, domperidone, promethazine, prochlorperazine) block dopamine stimulation in the intestines and chemoreceptor trigger zone, limiting emetic input to the medullary vomiting center. Promethazine and prochlorperazine also inhibit central muscarinic and his- tamine receptors, which contributes to their antiemetic and sedative properties [125]. Ondansetron inhibits serotonin-5HT3 receptors in the small bowel, vagal nerve, and chemoreceptor trigger zone, suppress- ing serotonergic activation of the vomiting center to alleviate nausea and vomiting. Adverse effects are uncommon but can include headache, constipation, diarrhea, and fatigue [125].
Extrapyramidal symptoms, including irreversible tardive dyski- nesia (an involuntary movement disorder), are a potential risk with all central dopamine antagonists. Extended use (duration of 12 or more weeks) increases the risk of tardive dyskinesia [129]. However, dopamine antagonists are considered safe for use as acute therapy and are usually reserved for patients with severe vomiting [124]. In peripheral vestibular disorders, all vestibular suppressants can interfere with central compensation, and their use is rec- ommended to not exceed three days [15; 21; 128]. The goal is for patients to rapidly receive specialist care, but patients may not get an immediate appointment and remain highly symptomatic. In this context, vestibular suppressants should continue for symptom control until optimized treatment is initiated by a specialist [120]. Vestibular suppressants can cause drowsiness and interfere with driving. In particular, the use of benzodiazepines is a significant risk factor for falls; this risk increases with polyphar- macy, common in the elderly [15; 21]. Antihistamines carry added risks of impaired cognitive functioning, gastrointestinal motility, and vision in elderly patients [21]. Some patients can develop psychologic dependence to benzodiazepines and have difficulty discontinuing the medication [120].
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