Homatropine: Mechanism of Action, How to Use, Interactions, Intoxications and Utility

It is an antagonist of the quaternary ammonium muscarinic Acetylcholine receptor belonging to the group of drugs called Antimuscarinics.

Homatropine is used to treat duodenal or stomach ulcers and intestinal problems. It can be used together with antacids or another medication in the treatment of peptic ulcer. It can also be used to prevent nausea, vomiting and dizziness.

Mechanism of action

Homatropine is an antagonist of the muscarinic quaternary ammonium acetylcholine receptor.

The muscarinic acetylcholine receptor mediates several cellular responses, including the inhibition of adenylate cyclase, the decomposition of phosphoinositides and the modulation of potassium channels through the action of G proteins.

Homatropine inhibits the Muscarinic actions of acetylcholine in the structures innervated by postganglionic cholinergic nerves, as well as in smooth muscles that respond to acetylcholine but lack cholinergic innervation.

These sites of postganglionic receptors are present in the autonomous effector cells of the smooth muscle, the cardiac muscle, the sinoatrial and atrioventricular nodules and the exocrine glands.

Depending on the dose, anticholinergics may reduce the motility and secretory activity of the gastrointestinal system, and the tone of the ureter and urinary bladder and may have a mild relaxing action on the bile ducts and gallbladder.


This medication is used before eye exams (for example, refraction), before and after certain ophthalmologies, and to treat certain eye conditions (for example, Uveitis ).

Homatropine hydrobromide works by dilating the pupil of the eye.

How to use Homatropina?

Presentation in Drops

  • To avoid contamination, do not touch the tip of the dispenser, preventing it from coming in contact with your eye or any other area.
  • If you wear contact lenses, remove them before using eye drops.
  • Wait at least 15 minutes before replacing your contact lenses.
  • After the application do not open your eyes for 1-2 minutes.
  • This will prevent the medication from running out.
  • Try not to blink and do not rub your eye.
  • Repeat these steps for your other eye if so indicated or if your dose is for more than 1 drop.
  • If you are using this medicine on a regular schedule, apply it usually 2 to 3 times a day, every 3 to 4 hours, or as directed by your doctor.
  • Do not rinse the dispenser. Replace the dispenser cap after each use.
  • Do not use the solution if it turns brown or cloudy or if it contains particles.
  • Use eye drops before eye ointments to allow the drops to enter the eye.
  • Consult a health professional if your condition does not improve or if it gets worse.

Presentation Tablets or Via Oral

  • Take this medication orally, with or without food, usually every 4 or 6 hours, as needed or as directed by your doctor.
  • The dosage is based on your age, medical condition and response to therapy.
  • Follow your doctor’s instructions closely. The manufacturer recommends that adults do not take more than 6 tablets or 6 teaspoons (30 milliliters) per day. Children 6-12 years of age should not take more than 3 tablets or 3 teaspoons (15 milliliters) per day.
  • If you are taking the syrup, measure the dose carefully with a measuring device or special spoon.
  • Do not use a spoon for domestic use.
  • Do not increase your dose or use this medication more often or for longer than prescribed.
  • Your condition will not improve faster and your risk of side effects will increase.
  • This medication may cause withdrawal reactions, especially if it has been used regularly for a prolonged period or in high doses.

In such cases, the symptoms are:

  • Abstinence or restlessness
  • Runny nose.
  • Lachrymation
  • Difficulty to sleep.
  • Severe abdominal / muscle pain.
  • Sickness.
  • Vomiting
  • Accelerated breathing and accelerated heart rate.

Interactions of Homatropine with other medications

Before using this medication, consult a health professional or specialist about all over-the-counter / herbal medications you can use, especially:

  • Certain antiarrhythmic medications (eg, quinidine).
  • Antihistamines (eg, diphenhydramine, meclizine).
  • Antispasmodics (eg, dicyclomine).
  • Certain drugs for Parkinson’s disease (for example, anticholinergics such as benztropine, trihexyphenidyl).
  • Inhibitors of MAO (isocarboxazid, linezolid, methylene blue, moclobemide, phenelzine, procarbazine, rasagiline, safinamide, selegiline, tranylcypromine).
  • Other medications for the eyes, tricyclic antidepressants (eg, amitriptyline ).

Therefore, before using this product, consult a health professional or specialist about all the products you use. Keep a list of all your medications with you and share the list with your doctor and specialist.


Symptoms of an overdose may include:

  • Reddened / dry skin.
  • Blurry vision.
  • Accelerated / irregular heartbeat.
  • Fever.
  • Mental / mood changes (eg, hallucinations)
  • Loss of coordination.

Other uses of Homatropina – Utility

This medication is also used to relieve dry cough, usually caused by the common cold or other conditions as prescribed by your doctor. Relieving cough helps you rest and sleep more.

This product contains 2 medications, hydrocodone and homatropine. Hydrocodone is a narcotic cough suppressant (antitussive) that works in certain brain centers to stop the need to cough. Homatropine belongs to a class of medications known as anticholinergics.

This medication is usually used for short-term treatment. It should not be used for persistent cough due to smoking or long-term respiratory problems (eg, asthma , emphysema ) or for coughs with a lot of mucus or fluids (productive cough), unless directed by your doctor.

To prevent withdrawal reactions, your doctor may reduce your dose gradually.

Consult your doctor or specialist for more information and report any abstinence reactions immediately.

Although it helps many people, this medication has a risk of abuse and can sometimes cause addiction.