Meclizine may be given to help control nausea and vomiting that often occurs with cancer treatment, other medical conditions or motion sickness.
Meclizine acts as a central nervous system depressant. It is believed its therapeutic actions occur due to the drug's drying effects and its ability to depress conduction of nerve messages in the inner ear. Meclizine begins working about one hour after ingestion. It continues being effective for eight to 24 hours.
The dosage to control nausea and vomiting associated with cancer treatment is 25 mg to 50 mg, every eight to 12 hours. When used to manage dizziness, patients generally take 25 mg to 100 mg daily in divided doses. Patients should not double up on this medication if a dose is missed.
Patients with glaucoma, an enlarged prostate, bladder or bowel obstructions, or asthma or other breathing difficulties should discuss with the doctor the risks and benefits associated with this drug before taking it. Those who have experienced an allergic reaction to meclizine should not take it. Meclizine's effects on children are not documented. Therefore, youngsters under age 12 should not take this drug, except under the direction of a physician. Pregnant women and those trying to become pregnant should not take this medication. Animal reproductive studies have shown some deformities at elevated doses. Women who are breastfeeding should discuss this medication with their doctor prior to taking it.
Meclizine may cause drowsiness and fatigue. Drowsiness is the most common adverse reaction. Alcohol and other central nervous system depressants, such as pain medication and tranquilizers, may increase this effect. Patients should refrain from drinking alcoholic beverages, and avoid driving or operating machinery or appliances when taking this drug. Less frequently, the drug also may produce the opposite effect. Excitability, nervousness, restlessness, mood enhancement and difficulty sleeping may develop. Rarely, it may cause a patient to see or hear things that are not present (halluci-nations). Despite being used to treat nausea and vomiting, it may produce this effect. It may also cause constipation, diarrhea, an upset stomach or a poor appetite (anorexia). Other side effects include frequent or difficult urination, incomplete emptying of the bladder, low blood pressure, a rapid heart rate or palpitations. It may cause vision changes, a dry nose and throat, ringing in the ears, and a rash or hives. Some of the side effects may be more pronounced in older adults.
Side effects may decrease as the body adjusts to the medication. Ice chips or sugarless hard candy or gum may help relieve the dry mouth. If the feeling of a dry mouth persists for more than two weeks, the doctor should be notified.
Central nervous system depressants, including alcohol, may increase drowsiness associated with meclizine. Pain medications, other antihistamines, seizure medications, sleeping pills and muscle relaxants can depress the central nervous system. Taking this drug with some medications used to treat depression may increase the risk of side effects. Patients should inform the doctor of all medications being taken. Patients should not start or stop any drugs without the approval of the doctor. The herbal supplement henbane may increase some of meclizine's side effects, including dry mouth and difficulty urinating.
Debra Wood, R.N.
—Agent that blocks or counteracts the action of histamine, which is released during an allergic reaction.