Tacrine is an active ingredient in the discontinued medication Cognex that is a centrally acting anticholinesterase that was prescribed to combat the memory loss associated with Alzheimer's disease.


Tacrine was used to treat the mental symptoms of the early stages of Alzheimer's disease. It was not intended as a cure or a method to halt the progression of the disease but it was found to improve the cognitive abilities of some patients. Of the many changes that take place in the brain as Alzheimer's disease progresses, Tacrine was prescribed to slow the breakdown of acetylcholine (ACh). This essential chemical messenger is part of the neural pathways that make the brain function correctly, and as Alzheimer's progresses it kills more and more ACh. This was one reason why Tacrine was not effective in the advanced stages of Alzheimer's disease, as there would not be enough new ACh for the slowing of its breakdown to make a significant difference. The root of why this medication was discontinued has to do with the finding that Tacrine caused liver problems. Cognex was withdrawn from the market in May 2012 because of these concerns. Previous to this, it was only available with a doctor's prescription.

As a discontinued medication, it is very unlikely that any patient suffering from the effects of Alzheimer's disease or its associated dementia would be prescribed Tacrine today. If for some reason Tacrine is still prescribed as a course of treatment for Alzheimer's, it should be taken only with extreme caution and with full consideration that the liver failure associated with the medication may prove to be more immediately fatal than the disease it is intended to combat. It should also be noted that there was no evidence found in its clinical trials that suggest that Tacrine does anything to affect the underlying processes that lead to dementia in Alzheimer's patients. When this drug was prescribed it was mandatory to take periodic blood tests in order to monitor the function of the liver. Failure to do so was potentially more fatal than the disease that Tacrine is intended to treat.

Condition Treated

  • Alzheimer's disease

Type of Medicine

  • Cholinesterase Inhibitor

Side Effects

Along with the intended effects of Tacrine, there were some unwanted effects. Some were obvious and could be discovered by the patient while others could only be found through blood tests or other evaluations by a physician. Those that took Tacrine were often under the direct care of a physician and needed to undergo periodic blood testing. When prescribed, the physician had to weigh the potentially serious side effects against the possible good that it could do.

Some of the more common side effects of the medication included loss of motor control and balance. It also induced diarrhea, nausea, and vomiting as well as having a severe impact on the appetite of the patient. Less commonly seen, but no less severe, side effects included seeing the patient develop circulatory system problems such as a rapid heartbeat, high blood pressure, or a radical slowing of the heartbeat. It was also known to cause fever and rashes in some patients, as well as occasional losses of consciousness.

Some of the rare but serious side effects include those in the following list:

  • Convulsions (seizures)
  • Jaundice
  • Difficult urination
  • Respiratory problems
  • Coughing
  • Change in stool color
  • Aggression
  • Irritability
  • Nervousness
  • Trembling
  • Slow movement
  • Stiffness in extremities

In addition to these side effects, there was a significant risk of an overdose, especially when the medication was self-administered by the patient who may have been suffering from cognitive impairment. Side effects that indicated an overdose included:

  • Profuse sweating
  • Profuse salivating
  • Convulsions (seizures)
  • Muscle weakness
  • Severe vomiting
  • Severe nausea
  • Low blood pressure
  • Shock

The administration of this medication required constant monitoring and testing by a physician to look for the following life-threatening side effects of Tacrine.

  • Liver failure
  • Jaundice
  • Toxic shock

Tacrine had certain side effects that were not considered cause for immediate medical attention and would often subside once the patient adjusted to taking the medication. As there was often close monitoring of patients afflicted with the early stages of Altzheimer's dementia these side effects could be treated if they were too long in duration or bothersome to the patient.

Some of the more common temporary side effects of Tacrine included:

  • Headache
  • Dizziness
  • Abdominal pain
  • Muscle aches
  • Indigestion

Although less commonly seen, Tacrine was known to induce the following temporary side effects:

  • General discomfort
  • Rapid breathing
  • Insomnia
  • Swelling of the feet
  • Belching
  • Runny nose
  • Increased salivation
  • Watering of eyes
  • Increased urination
  • Increased sweating
  • Flushing of skin

This is not a comprehensive list and other side effects are possible when using Tacrine to treat Alzheimer's. If a patient is still currently taking Tacrine and develops any of these side effects or any that are not listed, inform the prescribing physician immediately.


As with any medication, it was important to use Tacrine only as directed by a physician. This prescription-only medication was also often used only under direct supervision by a medical professional to ensure that the doses were taken correctly and at the correct times. The manufacturer included the following guidelines for average doses but they might vary based on the severity of the condition in the patient, their general health, or other factors. If there was any conflict, the guidelines prescribed by the doctor were to be followed.

The medication was taken as an oral dose in capsule form. Each 10-milligram capsule was taken four times a day for the treatment of Alzheimer's disease. It was within the guidelines for the prescribing physician to increase the dose gradually if positive results were observed and no adverse effects on the liver were detected. However, the maximum dose was usually 40 mg capsules four times per day. In the event of a missed dose, it was recommended that it was taken as soon as possible after the missed dose unless it was time to take the next dose. It was important to stay on the dosing schedule as much as possible and double dosing was prohibited.

Guidelines for taking the medication also noted that it should only be taken with a glass of water and well between mealtimes. If the medication should cause an upset stomach, it was recommended that it be taken with as small an amount of food as possible.


Tacrine was known to create certain effects when combined with other medications, supplements, and substances. In some cases, it was deemed necessary to combine these drugs or supplements even though an adverse reaction could occur. Doctors often needed to decide if doses needed to be changed, prescriptions needed to be replaced, or treatments needed to be eliminated. When taking this medicine, it was imperative that the physician be aware of any medicines listed below that were being taken at the same time as Tacrine. These were some of the more significant interactions that could occur and this list is not comprehensive.

The following medications were not recommended to be used with Tacrine:

  • Bupropion
  • Donepezil
  • Pixantrone

Some medicines were known to induce side effects but may have been deemed necessary given the condition of the patient. These risks could be mitigated by adjusting doses of either or both medications.

  • Estradiol
  • Fluvoxamine
  • Haloperidol
  • Levonorgestrel
  • Riluzole
  • Theophylline

Certain other interactions were also known to cause a poor reaction when used with Tacrine. Primary among them was tobacco use, but alcohol and eating certain foods at the same time the dose was taken was also known to impact its effectiveness. This was why it was generally recommended that the doses be taken between mealtimes rather than with food or drink.


The primary concern with the use of Tacrine was its potential effects on the liver, and while taking the drug it was mandatory to have the blood of the patient tested biweekly and for progress to be checked at regular visits. The regular blood testing schedule was recommended to last at least 4 weeks and up to 16 weeks. However, this testing was often needed for the duration of use of the medicine. Even if all blood tests were normal, regular check-ups were required to evaluate the effectiveness of the medication on cognitive processes. There was also a potential for the symptoms of Alzheimer's to get worse rather than better under the influence of this medication. There was a known interaction with anesthetics and other common drugs used in surgery that made these drugs more powerful than they would normally be. Informing the doctor, dentist, or anesthesiologist prior to any procedure was recommended.

Tacrine was known to cause dizziness, clumsiness, and unsteadiness in some patients. Driving or operating machinery while taking it was discouraged as this could cause a potentially hazardous condition.

One of the dangers of this medication was its potential to be ceased without direction from the prescribing physician. Stopping or starting Tacrine too suddenly was known to cause severe mental or behavioral changes in the patient. Because of the nature of Alzheimer's disease, there was also a significant danger of overdose associated with Tacrine if not taken under the direct supervision of medical staff. Such overdoses could lead to potentially serious side effects such as seizures or shock. Patients needed to be monitored for any of the signs of an overdose, including dilated pupils, increased sweating, irregular breathing, a weak pulse, and vomiting.

There was a significant potential for allergic reactions to Tacrine. Some of the symptoms of allergic reactions were similar to those experienced by patients who had suffered an overdose.

One of the concerns with Tacrine is that there is a poverty of data regarding its effects on pediatric patients, young adults, and pregnant or nursing mothers as it has only ever been tested on elderly adults. If Tacrine is taken by any of these people it is to be treated as a poison incident as the potential risks are unknown.

Certain medical problems may cause complications when combined with Tacrine. A history of the following medical conditions may cause adverse reactions to the drug, including a recurrence or worsening of the condition:

  • Asthma
  • Heart problems
  • Hypertension
  • Heart murmurs
  • Intestinal blockage
  • Liver disease
  • Parkinson's disease
  • Stomach ulcers
  • Urinary tract blockage
  • Brain disease
  • Epilepsy
  • Seizures
  • Head injury


General guidelines for the storage of medication applied to Tacrine. The pills were advised to be stored in a closed container at all times at room temperature. It was suggested that the medication be kept away from heat, moisture, and direct sunlight. In addition, the medication was to be kept away from freezing temperatures. If still held in possession, it is very important that this medication be kept out of the reach of children and securely kept away from anyone who is not prescribed this medication. It is recommended that old or expired Tacrine be disposed of immediately.


Tacrine had a short but eventful history as one of the first treatments for Alzheimer's disease. It treated patients suffering from mild to moderate dementia, impairment of judgment, degradation of memory, changes in personality, and other cognitive impairments brought on by Alzheimer's disease. In this initial phase of use, it showed significant promise for both Alzheimer's patients and their families. Marketed under the name Cognex, it was a cholinesterase inhibitor that provided an innovative treatment capable of slowing the breakdown of acetylcholine (ACh) within the brain. At the time, it represented a great leap forward in the treatment of the fatal disease.

One of the notable difficulties facing Cognex was the general poor health experiences in patients that are suffering from Alzheimer's. Generally of advanced age, patients often had many health problems that were exacerbated by treatment with the medication. In addition, many of its more intense side effects made the general health of patients worse even as it increased or preserved their mental state, often hastening their entry into assisted living situations rather than delaying it. It was also not found to address the underlying problems that led to dementia and in some cases could make the mental state of the patient worse instead of better.

These factors, among others, were what ultimately led to the medication being discontinued and no longer prescribed for the treatment of patients who were suffering from Alzheimer's disease. While treatment of patients with Tacrine may have yielded some positive results, its severe effect on the liver of patients is what led to it being discontinued. It was a side effect that required constant and close monitoring in order to prevent a potentially fatal condition. In the treatment of dementia experienced by Alzheimer's patients, it has generally been replaced with safer options. Its beneficial effect of preventing the breakdown of ACh was also a temporary measure to combat a permanent problem and the potentially fatal side effects of the drug led to it being pulled from the market.

Last Reviewed:
December 23, 2017
Last Updated:
February 10, 2018
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