What Is Acetylcholine?
Acetylcholine is a parasympathomimetic drug that is used for ophthalmological applications. Parasympathomimetic drugs are also called cholinomimetic drugs, and these activate the parasympathetic nervous system (PSNS).
The sympathetic nervous system is a part of the brain that is involved in the "fight or flight" response, and the PSNS is the "rest and digest" side.
The PSNS uses acetylcholine, a neurotransmitter (chemical messenger) that helps in brain-body coordination. Cholinomimetic drugs delay the breakdown or promote the release of acetylcholine.
What is Acetylcholine Used For?
Acetylcholine in drug form is available as eye drops. It is used to create rapid miosis (shrinking of the pupil) during cataract surgery after the lens is placed or during general eye surgery.
This drug has no value when intravenously administered as it is quickly deactivated by a group of enzymes in the Central Nervous System called cholinesterase. The eye drop form, however, helps quicken recovery after eye surgery.
How Does Acetylcholine Work?
When administered inside the eyes, Acetylcholine controls nerve impulse transmission and causes rapid shrinking of the pupil.
A nerve impulse is the way nerve cells (neurons) communicate with one another. Nerve impulses are mostly electrical signals.
About 0.5-2 ml of the 1% solution is introduced into the eyes, and miosis occurs (pupil shrinks to less than 2mm). Miosis lasts for about 10 minutes
Side Effects Of Acetylcholine
Some common side effects of acetylcholine are:
- Corneal edema (inflammation of the cornea)
- Corneal clouding
- Corneal decompensation (opacity of the cornea)
Rarer side effects of acetylcholine are:
- Breathing difficulties
- Low blood pressure
- Excessive sweating
- Flushing
- Low heart rate (bradycardia)
Interactions With Other Drugs
Acetylcholine can interact with certain drugs and lower the efficiency of the drug or cause extreme side effects. Therefore, make sure to notify your doctor if you are on any of the following drugs.
- Nonselective monoamine oxidase inhibitors (MAO inhibitors)
- Topical nonsteroidal anti-inflammatory agents
- Antihistamine drugs
- Colistin (antibacterial drug)
- Ganciclovir (antiviral drug)
Acetylcholine: Gene-Drug Interactions
Acetylcholine And ACE Gene
The ACE gene (angiotensin-converting gene) helps produce the ACE enzyme.
The ACE enzyme regulates blood pressure and fluid balance in the body by constricting the blood vessels.
In a study, researchers introduced enalaprilat, an ACE inhibitor drug, to 56 patients with atherosclerosis (a condition caused by the build-up of fat and cholesterol).
ACE inhibitor drugs interfere with the ACE enzyme activity and relax the blood vessels.
Image: Action of ACE Inhibitors
These patients were then administered acetylcholine. Changes in the coronary blood flow, vascular resistance, and epicardial diameter were then measured.
People with the DD and ID types of the ACE gene had a better blood flow and relaxation of blood vessels than those with the II type.
| Genotype | Implications |
| DD | Increased coronary blood flow |
| ID | Increased coronary blood flow |
| II | Lowered coronary blood flow |
Recommendations To Safely Use Acetylcholine
Usage Recommendations
As a topical eye solution, acetylcholine is very unstable. Therefore, the solution has to be prepared and used immediately.
Overdose Symptoms
Acetylcholine overdose can lead to cardiovascular complications or constriction of the airways. Drugs that can counteract this constriction effect have to be kept ready while administering acetylcholine.
Allergic Reactions
Rarely, some people can have an allergic response to acetylcholine and develop the below symptoms.
- Rashes
- Itching
- Hives
- Blisters in skin
- Breathing difficulties
- Swelling of throat, tongue, and lips
If you experience any of the above-mentioned symptoms when treated with acetylcholine, notify your doctor immediately.
Genetic Testing
Genetic testing can help understand how your body responds to acetylcholine. This can enable your doctor to administer the drug at correct dosages with proper precautions.
Analyze Your Genetic Response to Acetylcholine
Video
Summary
- Acetylcholine is a parasympathomimetic drug that is used to create miosis of the pupils during eye surgery.
- When administered intravenously, acetylcholine is quickly deactivated by a group of enzymes called cholinesterase.
- The common side effects of acetylcholine include corneal edema, clouding, and decompensation. Rarer side effects include excessive sweating, breathing difficulties, and lowered heart rate and blood pressure.
- The ACE gene that regulates blood flow by constricting blood vessels influences how you respond to acetylcholine.
- Some people may be allergic to acetylcholine and develop allergy symptoms like hives, itching, rashes, and swelling of the throat, lips, and tongue.
- Acetylcholine overdose can lead to constriction of airways and cardiovascular complications.
- Genetic testing can help understand how your body may respond to acetylcholine and plan accurate doses for you.
References
- https://reference.medscape.com/drug/miochol-e-acetylcholine-343661#10
- https://en.wikipedia.org/wiki/Acetylcholine#Pharmacology
- https://go.drugbank.com/drugs/DB03128
- https://www.rxlist.com/consumer_acetylcholine_miochol_e/drugs-condition.htm
- https://www.rxlist.com/miochol-e-drug.htm#medguide
- https://www.news-medical.net/drugs/Miochol-E.aspx
- https://www.ncbi.nlm.nih.gov/medgen/184923 https://www.ahajournals.org/doi/full/10.1161/01.CIR.102.1.35
