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Carbachol (Monograph)

Brand names: Miostat, Isopto Carbachol
Drug class: Miotics
ATC class: S01EB02
VA class: OP102
CAS number: 51-83-2


Miotic; direct-acting parasympathomimetic agent.

Uses for Carbachol

Open-Angle Glaucoma

Reduction of elevated intraocular pressure (IOP) in patients with primary, open-angle (chronic simple, noncongestive) glaucoma.

Used mainly in patients refractory or hypersensitive to pilocarpine.

May use concomitantly with sympathomimetic agents, β-adrenergic blocking agents, or carbonic anhydrase inhibitors.

Ocular Surgery

Production of miosis during surgery on the anterior chamber of the eye (e.g., cataract extraction, keratoplasty, peripheral iridectomy, cyclodialysis).

Reduction of the intensity of IOP elevation for the first 24 hours after cataract surgery.

Intraocular acetylcholine generally preferred.

Angle-Closure Glaucoma

Reduction of IOP in the emergency treatment of acute (congestive) angle-closure glaucoma [off-label] prior to surgery.

Pilocarpine generally preferred.

Ophthalmologic Examinations

Production of miosis to counteract mydriatic effects of sympathomimetic agents (e.g., hydroxyamphetamine, phenylephrine) after ophthalmoscopic examinations [off-label] in glaucoma patients.

Pilocarpine generally preferred.

Carbachol Dosage and Administration


Ophthalmic Administration

Administer ophthalmic topical solution to the conjunctival sac; do not inject.

Administer intraocular injection by injection into the anterior chamber.

Topical Solution

Remove contact lenses before instilling solution.

To minimize adverse effects, begin with a low concentration and increase gradually as needed. Additionally, instill daily dose or one of the daily doses at bedtime.

Following topical instillation, apply finger pressure on the lacrimal sac for 1–2 minutes to minimize drainage into nose and throat and reduce risk of absorption and systemic reactions. Remove excess solution around the eye with a tissue and rinse off any medication on hands immediately.

Intraocular Injection

Instill into anterior chamber of the eye before or after securing sutures, following the manufacturer’s directions. Vials are for single-dose use only; discard unused portion.


Adjust concentration and frequency of solution instillation according to patient requirements and response, as determined by tonometric readings before and during therapy.

In patients with heavily pigmented irides, higher solution concentrations may be required.


Open-Angle Glaucoma
Ophthalmic Topical

1–2 drops of 1.5–3% topical solution up to 3 times daily.

Ocular Surgery

Inject ≤0.5 mL of a 0.01% solution.

Prescribing Limits


Ocular Surgery

Maximum: 0.5 mL of a 0.01% injection.

Special Populations

No special population dosage recommendations at this time.

Cautions for Carbachol




Systemic Toxicity

Systemic reactions (e.g., salivation, syncope, cardiac arrhythmia, epigastric distress, headache, vomiting, asthma, hypotension, diarrhea, urinary urgency, increased sweating) reported rarely after topical application or intraocular injection; usually occur only with very frequent administration.

Use cautiously in patients with acute cardiac failure, bronchial asthma, active peptic ulcer, hyperthyroidism, GI spasm, urinary tract obstruction, Parkinson’s disease, recent MI, or systemic hypertension or hypotension.

Use topical solution cautiously in presence of corneal abrasion to avoid excessive penetration and systemic toxicity.

If systemic symptoms occur, discontinue drug, at least temporarily.

Ocular Toxicities

Retinal detachment reported rarely; use with extreme caution, if at all, in patients with a history or risk of retinal detachment, especially if young or aphakic. Carefully examine retinal periphery at least annually to detect an impending detachment.

Intraocular injection: Corneal clouding, persistent bullous keratopathy, retinal detachment, and postoperative iritis reported following cataract extraction in some patients.

Sensitivity Reactions


Allergic conjunctivitis, dermatitis, or keratitis reported occasionally with miotics; usually alleviated by changing to another miotic. In some instances, allergic reactions may be caused by preservatives in the preparations.

Discontinue the drug if sensitivity develops or if original irritation persists or increases.

General Precautions

Ocular Effects (Topical Solution)

Possible spasm of accommodation and poor vision in dim light, particularly in geriatric patients and patients with lens opacities. (See Advice to Patients.)

Adverse effects often subside after first few days of therapy or if drug is temporarily discontinued. (See Administration under Dosage and Administration.)

Possible transient increase in IOP even when the angle is open. In some patients with angle-closure glaucoma receiving miotics, may increase IOP and precipitate acute attacks.

Possible lens opacities and cataracts; lens opacities may regress if therapy discontinued early in development; however, cataracts are often progressive.

Regular slit-lamp examinations recommended; discontinue therapy, at least temporarily, if iris cysts, iritis, synechiae, or lens opacities occur.

Specific Populations


Category C.


Not known whether carbachol is distributed into milk. Use with caution.

Pediatric Use

Safety and efficacy not established.

Geriatric Use

Reduced visual acuity in dim light is common in geriatric patients. (See Ocular Effects [Topical Solution] under Cautions.)

Common Adverse Effects

Topical solution: Ocular irritation (burning or discomfort), lacrimation, temporal or periorbital headache, painful ciliary or accommodative spasm, blurred vision or myopia, conjunctival vascular congestion, poor vision in dim light.

Drug Interactions

Specific Drugs




Miotics, anticholinesterase

Possible antagonism

Concomitant use of miotics not recommended; unresponsiveness to both drugs may develop

Increased risk of allergic reactions and toxicity

Ocular hypotensive agents (e.g., carbonic anhydrase inhibitors, topical epinephrine, topical timolol)

Additive IOP lowering effects

Used to therapeutic advantage

Carbachol Pharmacokinetics



Topical carbachol penetrates intact corneal epithelium very poorly; penetration greatly improved in combination with wetting agent (e.g., benzalkonium chloride 0.003%).

May be absorbed through intact skin.


Topical solution: Miosis occurs within 10–20 minutes; maximal reduction in IOP occurs within 4 hours.

Intraocular injection: Maximal miosis occurs within 2–5 minutes.


Topical solution: Miosis persists for 4–8 hours; reduced IOP persists for approximately 8 hours (3% solution has a slightly longer duration of action than lower concentrations).

Intraocular injection: Miosis persists for about 24 hours.




Topical Solution


Intraocular Injection

15–30°C; protect from freezing and excessive heat. Stable for 18 months after the date of manufacture.


Advice to Patients


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.

* available from one or more manufacturer, distributor, and/or repackager by generic (nonproprietary) name



Dosage Forms


Brand Names





Injection, for intraocular use only

100 mcg/mL (0.01%)

Miostat Intraocular




Isopto Carbachol (with benzalkonium chloride; viscous)



Isopto Carbachol (with benzalkonium chloride; viscous)


AHFS DI Essentials™. © Copyright 2024, Selected Revisions May 1, 2008. American Society of Health-System Pharmacists, Inc., 4500 East-West Highway, Suite 900, Bethesda, Maryland 20814.

† Off-label: Use is not currently included in the labeling approved by the US Food and Drug Administration.

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