Alzheimer's disease is a progressive drain disorder that causes dementia, which includes memory loss and intellectual difficulties. A patient with Alzheimer's can forget common information such as his address and route home. In some cases, patients forget their own names, as well as those of people they have known for years. Memantine, galantamine and donezepil are medications used to treat Alzheimer's disease, and each has its own set of side effects.
Memantine
According to Drugs.com, side effects that are common with memantine use include diarrhea, nausea, vomiting, a fast heartbeat (tachycardia) and joint pain. Frequent rounds of diarrhea and vomiting can become dangerous if the patient becomes dehydrated and hypokalemic, a condition identified by a patient's low blood potassium levels. Memantine may also lower platelet counts (thrombocytopenia), which can result in fewer blood clots and make the patient prone to bruising and bleeding. Memantine's potentially fatal side effects include difficulty breathing, chest tightness, seizures and elevated blood pressure (hypertension).
Galantamine
MedlinePlus states that galantamine inhibits the breakdown of acetylcholine, a chemical in the brain needed for thinking and memory. Galantamine's common side effects include heartburn, stomach pain, diarrhea, vomiting, a runny nose, depression and trouble sleeping. Acid reflux causes heartburn. This can be managed with the use of over-the-counter antacids. Galantamine's serious side effects include bloody vomit, red or black stools, shortness of breath and fainting. Blood in the stool or vomit signifies gastrointestinal bleed occurring. Low blood pressure typically causes a patient to faint because the brain isn't getting enough blood.
Donepezil
Drugs.com indicates that donepezil, like galantamine, prevents acetylcholine breakdown. Donepezil's common side effects include muscle cramps, loss of appetite, nausea, diarrhea and vomiting. It can also provoke seizures, black or bloody stools and coughing.
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