Acetylcholine (Monograph)

Drug class: Miotics
ATC class: S01EB09
VA class: OP102
CAS number: 51-84-3

Medically reviewed by Drugs.com on Dec 22, 2023. Written by ASHP.

Introduction

Acetylcholine, a direct-acting parasympathomimetic agent, is a miotic.

Acetylcholine Dosage and Administration

Administration

Acetylcholine chloride is administered only in solution by instillation into the anterior chamber of the eye to produce miosis during ophthalmic surgery. The drug should be reconstituted immediately before use by removing the protective cap from the commercially available two-chambered vial, giving the plunger-stopper a quarter turn and pressing to force the solvent and center rubber plug into the lower chamber, and shaking the vial gently to dissolve the solid. If the rubber plug cannot be forced down or is already in the lower chamber, or if the reconstituted solution is discolored or contains a precipitate, the vial should not be used. Reconstitution produces 2 mL of a solution containing 1% (1:100) acetylcholine chloride and 2.8% mannitol. After cleansing the plunger-stopper with 70% alcohol or other suitable germicide, the appropriate dose of acetylcholine chloride is drawn into a dry, sterile syringe with an 18- to 20-gauge needle; the needle is then replaced with a suitable atraumatic cannula for intraocular irrigation. Instillation should be gentle and parallel to the iris face and tangential to the pupil border; flushing of the solution from the anterior chamber after miosis occurs is not necessary because of the short duration of action of the drug. In cataract surgery, acetylcholine should be used only after delivery of the lens.

Dosage

The usual dose of acetylcholine chloride to produce miosis during surgery is 0.5–2 mL of the 1% injection (5–20 mg) instilled into the anterior chamber before or after securing one or more sutures. To maintain miosis, 2% pilocarpine or 0.25% physostigmine solution may be applied topically immediately after surgery before application of the dressing.

Cautions for Acetylcholine

The toxicity of intraocular acetylcholine is very low because of its rapid destruction; however, hypotension, bradycardia, flushing, breathing difficulties, and sweating have been reported rarely in patients receiving intraocular acetylcholine. Intraocular acetylcholine may rarely cause corneal edema, corneal clouding, and corneal decompensation. Iris atrophy may result with excessive concentrations of acetylcholine. Intraocular irrigation with the drug must be gentle; a forceful jet of solution may rupture the hyaloid, cause vitreous loss, or traumatize or cause perforation of the iris, especially if it is atrophic. Temporary lens opacities reportedly have occurred following instillation of acetylcholine chloride injection and were attributed to the osmotic effect of 5% mannitol which was present in the preparation administered.

Safety and efficacy of intraocular acetylcholine chloride in children have not been established.

Acetylcholine Pharmacokinetics

Following instillation of a 1% solution of acetylcholine chloride into the anterior chamber of the eye, miosis occurs promptly and persists for approximately 10 minutes.

Chemistry and Stability

Chemistry

Acetylcholine, a direct-acting parasympathomimetic agent, is a quaternary ammonium compound. Acetylcholine chloride occurs as white or off-white crystals or crystalline powder and is very soluble in water and freely soluble in alcohol. Following reconstitution as directed with the electrolyte diluent supplied by the manufacturer (in the upper chamber of the 2-chambered Univial which contains the drug in the lower chamber), solutions containing 1% (1:100) acetylcholine chloride and 2.8% of mannitol have a pH of 5–8.2, are isotonic, and have an osmolality of about 275–330 mOsm/kg.

Stability

Unreconstituted two-chambered vials of acetylcholine chloride for injection should be stored at 15–30°C and protected from freezing. Aqueous solutions of acetylcholine chloride are unstable, decomposed by heat, and incompatible with alkalis and acids. The reconstituted solution should be used immediately and any unused portion discarded.

Preparations

Excipients in commercially available drug preparations may have clinically important effects in some individuals; consult specific product labeling for details.

Please refer to the ASHP Drug Shortages Resource Center for information on shortages of one or more of these preparations.

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