Aceclidine

Mechanism of Action

Aceclidine is classified as a direct-acting muscarinic agonist, directly activating muscarinic acetylcholine receptors of the parasympathetic nervous system. Unlike quaternary ammonium compounds (e.g., acetylcholine, muscarine), aceclidine is a tertiary ammonium compound lacking a permanent charge, which ensures better penetration across biological barriers.

Stimulation of muscarinic receptors leads to the excitation of effector organs innervated by the parasympathetic nervous system: smooth muscle tone in internal organs increases, exocrine gland secretion is enhanced, and heart rate is decreased. Its pharmacological spectrum is similar to pilocarpine, but it exhibits lower toxicity, broadening its potential for systemic use.

Pharmacological Effects

Local Effect in Ophthalmology: Pupil constriction ( miosis ) and accommodation spasm lead to the opening of the iridocorneal angle and improved outflow of aqueous humor through the trabecular meshwork. Intraocular pressure decreases for up to 6 hours following a single instillation.

Resorptive (Systemic) Effect upon parenteral administration or ingestion:

• Increased smooth muscle tone of the gastrointestinal tract and urinary bladder
• Enhanced intestinal peristalsis
• Increased myometrial tone (uterine musculature)
• Stimulation of digestive gland secretion (salivary, gastric)
• Decreased heart rate (bradycardia), lowered blood pressure

It is clinically important to understand the indirect functional antagonism with myotropic antispasmodics (e.g., papaverine): these drugs exert opposite effects on smooth muscle tone through different sites of action—receptor-mediated action for aceclidine versus direct action on the cellular contractile apparatus for papaverine.

Indications

Topical (Ophthalmology):

• Open-angle glaucoma — drug of choice for lowering intraocular pressure
• Acute angle-closure glaucoma attack (as part of combination therapy)

Systemic (Oral, Subcutaneous):

• Intestinal atony — postoperative paresis, dynamic intestinal obstruction
• Bladder atony — neurogenic urinary retention
• Uterine hypotonia in the postpartum period
• Postpartum uterine hemorrhage (to enhance myometrial contractions and stop bleeding)

For gastrointestinal and bladder atony, it can be prescribed as an alternative or adjunct to anticholinesterase agents (e.g., neostigmine bromide).

Adverse Effects and Contraindications

Adverse effects are related to muscarinic receptor hyperstimulation and occur predominantly with systemic administration:

• Hypersalivation (salivation), diarrhea
• Smooth muscle spasms (abdominal pain, frequent urination)
• Arterial hypotension, bradycardia
• Local irritation (burning sensation, conjunctival hyperemia upon eye drop instillation)

Contraindications (pathogenetically justified):

• Bronchial asthma and COPD — risk of bronchospasm due to increased bronchial smooth muscle tone
• Angina pectoris, bradycardia — exacerbation of cardiovascular pathology
• Peptic ulcer disease, hyperacid gastritis — stimulation of hydrochloric acid secretion aggravates the condition
• Pregnancy (except for the postpartum period) — increased myometrial tone creates a risk of miscarriage

Management of Complications: For arterial hypotension, $\alpha$-adrenergic agonists are administered to increase vascular tone.

Formulations and Prescription

Dosage Forms:

• Eye drops: 2%, 3%, 5% aqueous solutions
• Eye ointment: 3%, 5% — 20.0 g
• Injection solution: 0.2% in 1 mL and 2 mL ampoules

Dosing Regimen:

• Topical: 1–2 drops into the conjunctival sac 3–4 times daily
• Subcutaneous: 1–2 mL of 0.2% solution
• Maximum single and daily doses (MSD/MDD): 0.004 g / 0.012 g

Prescription Example (topical use):

Rp.: Sol. Aceclidini 3% — 10 ml D.S. Eye drops. Instill 2 drops into both eyes 3 times a day.

Prescription Example (parenteral administration):

Rp.: Sol. Aceclidini 0.2% — 1 ml D.t.d. N. 10 in amp. S. Administer subcutaneously 1 mL twice a day.

The drug is classified as a potent agent requiring careful handling. When prescribed systemically, the full spectrum of contraindications must be considered.