Donepezil: Formula, Presentation, Indications, Mechanism of Action, Dosage, Side Effects, Warnings, Contraindications and Interactions

It is an inhibitor of acetylcholinesterase, a cholinergic derived from piperidine.

The chemical formula of donepezil

  • C24H29NO3.


Donepezil is available as a 5 mg, 10 mg, and 23 mg oral tablet and 5 mg and 10 mg orally disintegrating tablet.


Donepezil is used to treat confusion ( dementia ) related to Alzheimer’s disease in mild or moderate forms.

Mechanism of action of donepezil

Donepezil works by inhibiting acetylcholinesterase; this results in increased acetylcholine levels in brain regions, which are decreased when suffering from Alzheimer’s disease, thus restoring the balance of neurotransmitters.


  • The starting dose of donepezil is 5 mg every 24 hours for at least one month.
  • Depending on the patient’s response, the dose can be progressively increased to 10 mg every 24 hours, the maximum daily amount.
  • This drug has not been studied in children and should not be used in children under 18.
  • Increasing the dose slowly gives the medicine time to work and reduces the risk of side effects.

Side effects of donepezil

Side effects that can occur with the use of donepezil include:

  • Fatigue
  • Sickness.
  • Diarrhea or constipation .
  • Headache.
  • Giddiness.
  • Anemiathrombocytopeniaeosinophilia.
  • Myalgia , arthralgia .
  • Insomnia .
  • Vomiting
  • Muscle cramps.
  • Fatigue.
  • Loss of appetite
  • Bruises
  • Weightloss.
  • Slow heart rate and fainting.
  • Bradycardia, sinoatrial block, and atrioventricular block.
  • Stomach ulcers and bleeding
  • Acidity.
  • Stomach ache.
  • Blood in vomit or dark-colored vomit that looks like coffee grounds.
  • Black stools.
  • Increase in lung diseases in patients with asthma or with any lung disease.
  • Seizures
  • Difficulty urinating.

Warnings and Contraindications

Special considerations should be made in dosing donepezil in people with liver problems.

If the liver is not working well, more of this drug can stay in the body longer, increasing the risk of side effects.


You should not take this medicine if you are allergic to donepezil or some of the other ingredients of the drug.

Before using this medicine, the medical history of the patient should be informed to the doctor, especially in cases of:

  • Kidney problems
  • Serious urinary tract infections.
  • Recent dietary change (from a high protein diet to a vegetarian diet).
  • Gastrointestinal disorders, stomach or intestinal diseases such as bleeding, peptic or duodenal ulcers.
  • Prostatic hypertrophy, urinary obstruction, difficulty urinating due to an enlarged prostate.
  • Epilepsy or some risk of seizures.
  • Breathing problems include asthma, chronic obstructive pulmonary disease, or other chronic obstructive pulmonary disorder.
  • Heart problems or a family history of specific heart problems such as QT prolongation on EKG, heart failure, slow heart rate, or sudden cardiac death.
  • Muscle-type disorders.
  • Hypothyroidism problems.

This product should only be used when necessary during pregnancy, so the risks and benefits should be discussed with the doctor.

It is not known if this product passes into breast milk, so it is recommended to stop breastfeeding or avoid administering this drug while breastfeeding.

Donepezil interactions

The risk of QT prolongation increases when potassium or magnesium levels fall in the blood, and this may increase if you use certain medications such as diuretics or ‘water pills’ or if you have conditions such as severe sweating, diarrhea, or vomiting; therefore use of these medications with donepezil should be avoided.

Donepezil causes drowsiness, so you should not drive, use machinery, or do anything that needs alertness until you can safely do so. Using alcohol or marijuana with donepezil can increase these effects.

Drug interactions can change the way they work or increase the risk of more severe side effects.

Some products that may interact with this drug include:

  • Cholinergic (bethanechol, among others): there is a risk of additive toxicity.
  • Suxamethonium: increases the possibility of muscle relaxant effects being increased.
  • Ketoconazole and quinidine: concomitant use with donepezil may cause inhibition of liver metabolism.
  • Rifampicin, carbamazepine, phenytoin, phenobarbital (and possibly other enzyme inducers): since they reduce plasma levels of donepezil.
  • Non-steroidal anti-inflammatory drugs: such as ibuprofen and naproxen, among others.