Rivastigmine

Definition

Rivastigmine is a drug used to treat symptoms of Alzheimer's disease . In the United States, rivastigmine is sold as the brand name drug Exelon.

Purpose

Rivastigmine is used to treat symptoms of Alzeheimer's disease in individuals with mild to moderate illness. It has also been used to treat dementia caused by other conditions such as Lewy-body disease or following strokes. The drug may produce mild improvements in symptoms of thinking for a short period of time, but rivastigmine does not cure or stop progression of underlying diseases.

Description

The Food and Drug Administration approved rivastigmine in 2000 specifically for treating Alzheimer's disease. In Alzheimer's disease, some cells in specific regions of the brain die. Because of this cell death, these brain cells lose their ability to transmit nerve impulses. Brain cells normally transmit nerve impulses another by secreting various chemicals known as neurotransmitters .

Brain cells that make and secrete a neurotransmitter called acetylcholine are affected early in the course of Alzheimer's disease. Rivastigmine prevents the breakdown of acetylcholine in the brain, thus temporarily increasing its concentration. In doing so, rivastigmine may improve the thinking process by facilitating nerve impulse transmission within the brain.

Rivastigmine is available as capsules in four different strengths and as an oral solution for use by people who have difficulty swallowing. Unlike some other drugs used to treat Alzheimer's disease, the liver does not break down rivastigmine. As a result, it may be preferred in the treatment of people with Alzeheimer's disease who have liver disease.

Recommended dosage

The initial dosage of rivastigmine is 1.5 mg taken two times per day. If this dose is tolerated without difficulty, the dosage may be increased to 3 mg twice a day after at least two weeks at the lower dosage. Some people are unable to tolerate nausea, vomiting, anorexia, and weight loss that occur with higher dosages. If the drug does not cause significant adverse effects, the dose may be increased to 4.5 mg two times per day, followed by 6 mg two times per day. The dosage should be increased slowly, at two-week intervals. If side effects occur and cannot be tolerated, the drug may be stopped for several doses. When the drug is started again, the same dosage or the next lower dosage may be tried. The maximum daily dosage is 6 mg two times per day.

Precautions

Rivastigmine may slow heart rates, increase acid in the stomach, make urination difficult, cause breathing difficulties, and may possibly contribute to seizures . As a result, it should be used with close physician supervision and monitoring in people with certain heart conditions, those who are prone to stomach ulcers, people with bladder obstruction, individuals with asthma or chronic obstructive pulmonary disease, and people with a history of seizures disorders.

Individuals taking rivastigmine should be reassessed periodically to determine whether the drug is providing any benefits. If caregivers feel the drug is no longer beneficial, it may be stopped.

Side effects

The most frequent side effects associated with rivastigmine involve stomach upset. Nausea, vomiting, anorexia, heartburn, and weakness occur in more than 5% of people and at twice the rate of placebo pills. Dizziness and headaches also occur in more than 10% of people taking rivastigmine.

Other, less common, side effects are difficulty sleeping, confusion, depression, anxiety, sleepiness, hallucinations , tremors, fainting, aggression, constipation, gas, overwhelming fatigue , weight loss, increased sweating, and infections.

Interactions

Drugs such as dicyclomine may inhibit the effects of rivastigmine. Other drugs like bethanechol may possibly increase some of the side effects of rivastigmine. Rivastigmine may interact with some of the drugs used to relax muscles during surgery. The interaction increases the effects of both drugs.

Resources

BOOKS

Ellsworth, Allan J. Mosby's Medical Drug Reference. St. Louis, MO: Mosby, Inc, 1999.

Facts and Comparisons Staff. Drug Facts and Comparisons. 6th Edition. St. Louis, MO: Facts and Comparisons, 2002.

Novartis Staff. Exelon Package Insert. Basle, Switzerland: Novartis Pharma AG, 2001.

Kelly Karpa, RPh, Ph.D.