The P-I-E-N-O Parkinsn's List Drug Database

meclizine / Antivert^TM , Bonine^TM

ANTIEMETIC:

Antivertigo

Description: Meclizine is a piperazine-derivative antihistamine used as an antivertigo/antiemetic agent. Meclizine is structurally and pharmacologically similar to buclizine and cyclizine. Meclizine is used in the prevention and treatment of nausea, vomiting, and dizziness associated with motion sickness. Additionally, it has been used in the management of vertigo in diseases affecting the vestibular apparatus. However, the efficacy of meclizine in these conditions has not been established. While prophylactic use of meclizine is most effective in the treatment of motion sickness, other factors such as patient age, and type, severity, and duration of motion influence its effectiveness. It has been suggested that meclizine causes fewer anticholinergic effects than scopolamine. Meclizine was approved by the FDA in 1953.

Mechanism of Action: Although the mechanism by which meclizine exerts its antiemetic and antivertigo effects has not been fully elucidated, its central anticholinergic properties are partially responsible. The drug depresses labyrinth excitability and vestibular stimulation, and it may affect the medullary chemoreceptor trigger zone. It also possesses anticholinergic, antihistaminic, central nervous system depressant, and local anesthetic effects.

Pharmacokinetics: In general, antihistamines are well absorbed after oral administration. The onset of action of meclizine is about 1 hour, with effects lasting between 8-24 hours. Distribution of meclizine has not been fully characterized. Metabolism in humans is unknown, although animal studies suggest hepatic metabolism. The plasma half-life in humans is 6 hours. The amount of dosage adjustment required in patients with renal impairment is unknown. Elimination of meclizine is not fully established. Meclizine may be excreted into breast milk; however, it is not known whether it crosses the placenta.

CONTRAINDICATIONS/PRECAUTIONS:

Due to the anticholinergic effects of meclizine, precautions must be exercised in certain patient populations such as elderly patients. Patients with bladder obstruction, particularly of the bladder neck or prostatic hypertrophy can develop symptomatic urinary retention. Anticholinergic actions can cause an acute attack of narrow-angle glaucoma. A decrease in gastric motility and tone can aggravate GI obstruction and retention in patients with pyloroduodenal obstruction.

Caution should be used in patients with asthma or chronic obstructive pulmonary disease since anticholinergic actions can increase obstruction of respiratory passages secondary to effects on bronchial secretions.

Lactation can be inhibited during breast-feeding due to the anticholinergic effects of meclizine. While this agent may be excreted in breast milk, no problems have been documented in the infant.

DRUG INTERACTIONS: The CNS depressant effects of meclizine can be potentiated by concurrent use of ethanol or other CNS depressant agents such as benzodiazepines, barbiturates, tricyclic antidepressants, opiate agonists, skeletal muscle relaxants, and antihistamines.

Concurrent use of other anticholinergics can potentiate the anticholinergic effects of meclizine.

Antivertigo agents can mask the symptoms of ototoxicity and should be used cautiously with aminoglycosides.

Patients on digoxin therapy should be monitored for increased digoxin effects when receiving drugs with anticholinergic activity. Meclizine can increase the absorption of digoxin by decreasing gastrointestinal motility.

ADVERSE REACTIONS: Potentially serious side effects associated with the cardiovascular system include hypotension and sinus tachycardia. Several less severe side effects have been attributed to meclizine use such as blurred vision, insomnia, tinnitus, constipation, difficulty in urinating, and urinary retention. However, the most frequently reported side effects with meclizine are drowsiness, fatigue, and xerostomia (dry mouth). Most side effects reported with meclizine are attributable to the anticholinergic properties of this drug. Thus, all classic anticholinergic effects are possible.

PATIENT INFORMATION:

What do meclizine tablets or capsules do?

Meclizine (Antivert^TM , Bonine^TM ) is an antihistamine. It helps to prevent nausea, vomiting, or dizziness associated with motion sickness, and to treat or prevent vertigo (extreme dizziness or a sensation that you or your surroundings are tilting or spinning around). Generic meclizine tablets and capsules are available.

What should my doctor, dentist, or pharmacist know before I take meclizine?

They need to know if you have any of these conditions:

• asthma
• glaucoma
• prostate trouble
• stomach problems
• urinary problems
• an unusual or allergic reaction to meclizine, other medicines, foods, dyes, or preservatives
• breast-feeding

How should I take this medicine?

Take meclizine tablets or capsules by mouth. Follow the directions on the prescription label. Swallow the tablets or capsules with a drink of water (chewable tablets can be chewed or swallowed whole). If you are using meclizine to prevent motion sickness, take the dose at least 1 hour before travel. If meclizine upsets your stomach, take it with food or milk. Take your doses at regular intervals. Do not take your medicine more often than directed.

Special precautions for use in children:

This medicine is not for children under 12 years old.

What if I miss a dose?

If you miss a dose and are taking meclizine on a regular schedule, take it as soon as you can. If it is almost time for your next dose, take only that dose. Do not take double or extra doses.

What other medicines can interact with meclizine?

• alcohol
• barbiturate medicines for inducing sleep or treating seizures (convulsions)
• certain antibiotics given by injection
• digoxin
• medicines for anxiety or sleeping problems, such as diazepam or temazepam
• medicines for hay fever and other allergies
• medicines for mental depression
• medicines for movement abnormalities as in Parkinson's disease, or for gastrointestinal problems
• medicines for pain
• medicines that relax skeletal muscle

Tell your doctor or pharmacist: about all other medicines you are taking, including non-prescription medicines; if you are a frequent user of drinks with caffeine or alcohol; if you smoke; or if you use illegal drugs. These may affect the way your medicine works. Check before stopping or starting any of your medicines.

What side effects may I notice from taking meclizine?

Serious side effects with meclizine are rare; they include:

• fainting spells
• fast or irregular heartbeat (palpitations)

Call your doctor as soon as you can if you get any of these side effects.

Minor side effects with meclizine include:

• blurred vision
• constipation
• difficulty passing urine
• difficulty sleeping
• drowsiness, dizziness
• dry mouth
• headache
• stomach upset

Let your doctor know about these side effects if they do not go away or if they annoy you.

What do I need to watch for while I take meclizine?

If you are taking meclizine on a regular schedule, visit your doctor for regular checks on your progress.

You may get dizzy, drowsy or have blurred vision. Do not drive, use machinery, or do anything that needs mental alertness until you know how meclizine affects you. Do not stand or sit up quickly, especially if you are an older patient. This reduces the risk of dizzy or fainting spells. Alcohol can increase possible dizziness; avoid alcoholic drinks.

Meclizine may make your mouth dry. Chewing sugarless gum, sucking hard candy and drinking plenty of water may help. Visit your dentist regularly.

Where can I keep my medicine?

Keep out of the reach of children in a container that small children cannot open.

Store at room temperature between 15 and 30C (59 and 86F). Keep container tightly closed. Throw away any unused medicine after the expiration date.

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