Dosing and uses of Miostat (carbachol)
Adult dosage forms and strengths
intraocular solution
- 0.01%
topical solution
- 1.5%
- 3%
Glaucoma
1-2 gtt instilled into conjunctival sac three times daily
As a Miotic During Ocular Surgery
0.5 mL instilled into the anterior chamber before or after securing sutures
Administration
Topical solution: to reduce drainage to nose & throat, apply finger pressure to lacrimal sac following administration, remove excess solution from eye & hand
Intraocular Injection: Withdraw appropriate amount into a sterile disposable syringe through a 0.45-micron filter provided by manufacturer using a 21-gauge needle. Prior to administration, remove attached needle & filter from syringe & replace with a suitable atraumatic cannula for intraocular irrigation. Instillation should be gentle & parallel to the iris face & tangential to the pupil border. Discard unused portions.
Pediatric dosage forms and strengths
As in adults
Miostat (carbachol) adverse (side) effects
Frequency not defined
Ocular
- Corneal clouding
- Stinging (transient)
- Ciliary spasm
- Bullous keratopathy
- Persistent bullous keratopathy
- Postoperative iritis following cataract extraction
- Retinal detachment (rare)
- Corneal edema, drug effect prolonged miosis, eye inflammation, eye pain, intraocular pressure increased, ocular hyperemia, vision blurred, and visual impairment
Systemic
- Abdominal cramps
- Epigastric distress
- Flushing
- Arrhythmia
- Hypotension
- Syncope
- Epigastric stress
- Salivation
- Vomiting
- Asthma
- Diaphoresis
- Headache
- Sweating
- Tightness in urinary bladder
Warnings
Contraindications
Hypersensitivity
Acute iritis
Acute inflammatory disease of the anterior chamber
Cautions
Use caution in asthma, acute heart failure, corneal abrasion, hyperthyroidism, urinary tract obstruction, Parkinson's disease, active peptic ulcer, GI spasm
Does not penetrate cornea readily, benzalkonium chloride is added in some formulations to enhance corneal penetration (Isopto-Carbachol)
Topical ophthalmic solution produces transient ocular & frontal headache
Use with caution in patients undergoing general anesthesia
The vial stopper contains natural rubber (latex) which may cause severe allergic reactions
Pregnancy and lactation
Pregnancy category: C
Lactation: Excretion in milk unknown; use with caution
Pregnancy categories
A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.
B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.
C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.
D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.
X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.
NA: Information not available.
Pharmacology of Miostat (carbachol)
Mechanism of action
Stimulates cholinergic receptors in the eye and in turn causes miosis
Pharmacokinetics
Duration:4-8 hr (reduction in intraocular pressure with ophthalmic instillation); 24hr (intraocular administration)
Onset: miosis: 2-3 min ((intraocular inj); ; 10-20 min (ophthalmic instillation)
