In the U.S.—

Other commonly used names are THA; tetrahydroaminoacridine.

• Dementia symptoms treatment adjunct

Tacrine (TAK-reen) is used to treat the symptoms of mild to moderate Alzheimer's disease. Tacrine will not cure Alzheimer's disease, and it will not stop the disease from getting worse. However, tacrine can improve thinking ability in some patients with Alzheimer's disease.

In Alzheimer's disease, many chemical changes take place in the brain. One of the earliest and biggest changes is that there is less of a chemical messenger called acetylcholine (ACh). ACh helps the brain to work properly. Tacrine slows the breakdown of ACh, so it can build up and have a greater effect. However, as Alzheimer's disease gets worse, there will be less and less ACh, so tacrine may not work as well.

Tacrine may cause liver problems. While taking this medicine, you must have blood tests regularly to see if the medicine is affecting your liver.

This medicine is available only with your doctor's prescription, in the following dosage form:

Oral
• Capsules (U.S.)

In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For tacrine the following should be considered:

Allergies—Tell your doctor if you have ever had any unusual or allergic reaction to tacrine or to wound antiseptics (e.g., Akrinol, Panflavin, Monacrin). Also tell your health care professional if you are allergic to any other substances, such as foods, preservatives, or dyes.

Pregnancy—Studies on effects in pregnancy have not been done in either humans or animals.

Breast-feeding—It is not known whether tacrine passes into breast milk. However, use of tacrine is not recommended in nursing mothers.

Children—Studies on this medicine have been done only in adult patients, and there is no specific information comparing use of tacrine in children with use in other age groups.

Older adults—Studies on tacrine have been done only in middle-aged and older patients. Information on the effects of tacrine is based on these patients.

Other medicines—Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. When you are taking tacrine, it is especially important that your health care professional know if you are taking any of the following:

• Cimetidine (e.g., Tagamet)—Cimetidine may cause higher blood levels of tacrine, which may increase the chance of side effects

• Inflammation or pain medicine, except narcotics—Stomach irritation may be increased

• Neuromuscular blocking agents (medicines used in surgery to relax muscles)—Tacrine may increase the effects of these medicines; your doctor may change the dose of tacrine before you have surgery

• Smoking tobacco—Smoking may cause lower blood levels of tacrine, which may decrease the effects of tacrine; if you smoke, your doctor may need to change the dose of tacrine

• Theophylline (e.g., Theo-Dur, Uniphyl)—Tacrine may cause higher blood levels of theophylline, which may increase the chance of side effects; your doctor may need to change the dose of theophylline

• Asthma (or history of) or
• Heart problems, including slow heartbeat or hypotension (low blood pressure), or
• Intestinal blockage or
• Liver disease (or history of) or
• Parkinson's disease or
• Stomach ulcer (or history of) or
• Urinary tract blockage or difficult urination—Tacrine may make these conditions worse

• Brain disease, other, or
• Epilepsy or history of seizures or
• Head injury with loss of consciousness—Tacrine may cause seizures

Take this medicine only as directed by your doctor. Do not take more or less of it, and do not take it more or less often than your doctor ordered. Taking too much may increase the chance of side effects, while taking too little may not improve your condition.

Tacrine is best taken on an empty stomach (1 hour before or 2 hours after meals). However, if this medicine upsets your stomach, your doctor may want you to take it with food.

Tacrine seems to work best when it is taken at regularly spaced times, usually four times a day.

Dosing—

The dose of tacrine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of tacrine. If your dose is different, do not change it unless your doctor tells you to do so.

• For oral dosage form (capsules):
  • For treatment of Alzheimer's disease:
    • Adults—To start, 10 milligrams (mg) four times a day. Your doctor may increase your dose gradually if you are doing well on this medicine and your liver tests are normal. However, the dose is usually not more than 40 mg four times a day.

Missed dose—

If you miss a dose of this medicine, take it as soon as possible. However, if it is within 2 hours of your next dose, skip the missed dose and go back to your regular dosing schedule. Do not double doses.

Storage—

To store this medicine:

• Keep out of the reach of children.
• Store away from heat and direct light.
• Do not store in the bathroom, near the kitchen sink, or in other damp places. Heat or moisture may cause the medicine to break down.
• Do not keep outdated medicine or medicine no longer needed. Be sure that any discarded medicine is out of the reach of children.

It is important that your doctor check your progress at regular visits. Also, you must have your blood tested every other week for at least the first 4 to 16 weeks when you start using tacrine to see if this medicine is affecting your liver. If all of the blood tests are normal, you will still need regular testing, but then your doctor may decide to do the tests less often.

Tell your doctor if your symptoms get worse, or if you notice any new symptoms.

Before you have any kind of surgery, dental treatment, or emergency treatment, tell the medical doctor or dentist in charge that you are taking this medicine. Taking tacrine together with medicines that are sometimes used during surgery or dental or emergency treatments may increase the effects of these medicines.

Tacrine may cause some people to become dizzy, clumsy, or unsteady. Make sure you know how you react to this medicine before you do anything that could be dangerous if you are dizzy, clumsy, or unsteady.

Do not stop taking this medicine or decrease your dose without first checking with your doctor. Stopping this medicine suddenly or decreasing the dose by a large amount may cause mental or behavior changes.

If you think you or someone else may have taken an overdose of tacrine, get emergency help at once. Taking an overdose of tacrine may lead to seizures or shock. Some signs of shock are large pupils, irregular breathing, and fast weak pulse. Other signs of an overdose are severe nausea and vomiting, increasing muscle weakness, greatly increased sweating, and greatly increased watering of the mouth.

Along with its needed effects, a medicine may cause some unwanted effects. Some side effects will have signs or symptoms that you can see or feel. Your doctor may watch for others by doing certain tests

Tacrine may cause some serious side effects, including liver problems. You and your doctor should discuss the good this medicine will do as well as the risks of receiving it.

Check with your doctor as soon as possible if any of the following side effects occur:

• More common
  • Clumsiness or unsteadiness;  diarrhea ;  loss of appetite;  nausea ;  vomiting 
  
  

• Less common
  • Fainting;  fast or pounding heartbeat ;  fever;  high or low blood pressure;  skin rash;  slow heartbeat 
  
  

• Rare
  • Aggression, irritability, or nervousness;  change in stool color;  convulsions (seizures);  cough, tightness in chest, troubled breathing, or wheezing;  stiffness of arms or legs, slow movement, or trembling and shaking of hands and fingers;  trouble in urinating;  yellow eyes or skin 
  
  

• Symptoms of overdose
  • Convulsions (seizures);  greatly increased sweating;  greatly increased watering of mouth;  increasing muscle weakness;  low blood pressure;  nausea (severe);  shock (fast weak pulse, irregular breathing, large pupils);  slow heartbeat;  vomiting (severe) 
  
  

This medicine may also cause the following side effect that your doctor will watch for:

• More common
  • Liver problems 
  
  

Other side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. However, check with your doctor if any of the following side effects continue or are bothersome:

• More common
  • Abdominal or stomach pain or cramping;  dizziness;  headache;  indigestion ;  muscle aches or pain 
  
  

• Less common
  • Belching;  fast breathing;  flushing of skin;  general feeling of discomfort or illness;  increased sweating;  increased urination;  increased watering of eyes;  increased watering of mouth;  runny nose;  swelling of feet or lower legs;  trouble in sleeping 
  
  

Other side effects not listed above may also occur in some patients. If you notice any other effects, check with your doctor.