Meclizine HCl – Nicotinic Acid
Action And Clinical Pharmacology: Meclizine has antihistaminic and anticholinergic properties. Nicotinic acid is a vasodilator agent which has been found effective in the treatment of vertigo due to cerebral arteriosclerosis.
The site and mechanism of action of meclizine in controlling vertigo arising from various conditions, have not been clearly defined. Pharmacological studies conducted with other antihistamines show that the peripheral labyrinthine structure may be the site of action.
Indications And Clinical Uses: For the treatment of vertigo, whether due to cerebral arteriosclerosis, labyrinthitis, vestibular dysfunction or other related conditions. Also useful in treating vascular headaches and radiation sickness.
Contra-Indications: Hypersensitivity to either meclizine or nicotinic acid.
Because of the vasodilation produced by nicotinic acid, severe hypotension and hemorrhage are contraindications to Antivert therapy.
Manufacturers’ Warnings In Clinical States: Occupational Hazards: Patients should be warned that Antivert may occasionally cause drowsiness and that when taking it they should take the necessary precautions against driving or operating dangerous machinery or when taking part in activities requiring mental alertness.
Patients suffering from glaucoma or prostatic enlargement should take Antivert only under the direction of a physician.
Precautions: Patients should be made aware of the frequent, short-lived reactions experienced with nicotinic acid therapy such as cutaneous flushing, sensations of warmth, tingling and itching, burning of the skin, increased gastrointestinal motility and sebaceous gland activity. These reactions are coincidental to the vasodilatation produced by nicotinic acid.
Pregnancy: One of the components of this combination product meclizine, as many other drugs of this class, has shown certain teratogenic effects (i.e., cleft palates) in the rat at doses of 25 to 50 times the human dose. These abnormalities have not been observed in other experimental animals, including the monkey.
The use of Antivert by women who are pregnant or may become pregnant requires that the potential benefits be weighed against the potential risks.
Drug Interactions: There may be increased CNS depression when Antivert is administered concomitantly with other CNS depressants, including barbiturates, alcohol, tranquilizers, and sedatives.
MAO inhibitors may prolong and intensify the anticholinergic effects of Antivert.
Adverse Reactions: Drowsiness, dry mouth, vomiting, fatigue and, on rare occasions, blurred vision have been reported with Antivert therapy.
Adverse effects associated with nicotinic acid include cutaneous flushing, sensations of warmth, tingling and itching, burning of the skin, increased gastrointestinal motility and sebaceous gland activity. These reactions are coincidental to the vasodilatation produced by nicotinic acid.
Symptoms And Treatment Of Overdose: Symptoms: In adults, the usual signs of meclizine overdose are CNS depression with drowsiness, coma and convulsions. Hypotension may also occur, particularly in the elderly. In children, anticholinergic effects and CNS stimulation (hallucinations, seizures, trouble sleeping) are more likely to occur.
Signs of nicotinic acid overdose are flushing, gastrointestinal upset, and pruritus.
Treatment: There is no specific antidote for treatment of meclizine overdosage. Symptomatic and supportive treatment should be employed. If ingestion is recent (within 1 hour), induce emesis (syrup of ipecac is recommended; precautions against aspiration are required, especially in infants and children) or empty stomach by gastric lavage if patient has been unable to vomit within 3 hours of ingestion. Activated charcoal may also be used. Keep patient calm to minimize excitation. Vasopressors (norepinephrine or phenylephrine) may be used to correct hypotension. Physostigmine may be useful to counteract the CNS anticholinergic effects of meclizine. Do not use stimulants. If vasopressors are indicated do not use epinephrine, because it may lower blood pressure further. Diazepam i.v. may be given for treatment of seizures that do not respond to physostigmine.
Dosage: One tablet 3 times a day before each meal. If excess flushing occurs, take Antivert immediately after meals.
Availability And Storage: Each blue, scored tablet contains: meclizine HCl 12.5 mg and nicotinic acid 50 mg. Nonmedicinal ingredients: calcium phosphate, cornstarch, magnesium stearate, polyethylene glycol, sucrose, talc and dye FD & C Blue #1. Tartrazine-free. Bottles of 100 and 500. Store between 15 and 30°C. (Shown in Product Recognition Section)
ANTIVERT Pfizer Meclizine HCl – Nicotinic Acid Vertigo Therapy