CYCLOGYL
Clinical safety rating: caution
Comprehensive clinical and safety monograph for CYCLOGYL (CYCLOGYL).
Blocks muscarinic acetylcholine receptors (M1-M5), inhibiting parasympathetic nerve impulses that cause constriction of the ciliary muscle and sphincter muscle of the iris, resulting in cycloplegia (ciliary muscle paralysis) and mydriasis (pupil dilation).
| Metabolism | Primarily metabolized by ester hydrolysis in the plasma and liver. |
| Excretion | Renal excretion of unchanged drug accounts for less than 5% of elimination; the majority is metabolized in the liver and excreted in urine as metabolites. Biliary/fecal excretion is minimal (<2%). |
| Half-life | Terminal elimination half-life is approximately 0.5 to 0.75 hours in adults; in children, it may be slightly shorter. Clinical context: short half-life allows repeated administration for mydriasis and cycloplegia. |
| Protein binding | Approximately 50-60% bound, primarily to albumin. |
| Volume of Distribution | Volume of distribution is approximately 2.5-4.0 L/kg after systemic absorption. However, systemic absorption following ophthalmic administration is minimal; Vd reflects distribution in the eye and systemic compartment. |
| Bioavailability | Ophthalmic: systemic bioavailability is very low due to local administration and first-pass metabolism in the nasopharynx after drainage. Estimated <1% systemically available. No oral formulation. |
| Onset of Action | Ophthalmic: mydriasis within 15-30 minutes, cycloplegia within 30-60 minutes. |
| Duration of Action | Mydriasis: 6-8 hours; cycloplegia: 24-48 hours (complete recovery may take several days). Clinical note: effects are prolonged in patients with heavily pigmented irides. |
1-2 drops of 0.5% or 1% solution in conjunctival sac, may repeat in 5-10 minutes if needed, up to every 4-6 hours.
| Dosage form | SOLUTION/DROPS |
| Renal impairment | No dose adjustment required. |
| Liver impairment | No dose adjustment required. |
| Pediatric use | 1 drop of 0.5% solution in conjunctival sac, may repeat in 5-10 minutes; maximum 0.5% solution for infants and children. |
| Geriatric use | Use lowest effective dose (0.5% solution) due to increased risk of adverse effects such as increased intraocular pressure and confusion. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for CYCLOGYL (CYCLOGYL).
| Breastfeeding | No data on excretion in human milk. M/P ratio unknown. Low systemic absorption suggests minimal risk, but caution advised. Avoid breastfeeding for 2 hours after instillation. |
| Teratogenic Risk | No adequate studies in pregnant women. Animal reproduction studies not available. Risk cannot be ruled out. Systemic absorption after ophthalmic administration is low, but may cause fetal effects due to anticholinergic activity. Avoid in first trimester if possible. |
| Fetal Monitoring |
■ FDA Black Box Warning
None.
| Serious Effects |
["Hypersensitivity to cyclopentolate or any component of the formulation","Untreated narrow-angle glaucoma or anatomically narrow angles","Should not be used in infants under 1 year of age for refraction purposes (due to risk of CNS effects)"]
| Precautions | ["Use with caution in patients with increased intraocular pressure or angle-closure glaucoma; may precipitate acute angle-closure glaucoma.","Can cause sensitivity reactions such as eye irritation, edema, and dermatitis.","Systemic absorption can cause central nervous system disturbances (hyperactivity, restlessness, hallucinations) especially in children; use lowest effective concentration.","In individuals with Down syndrome or brain damage, increased susceptibility to central nervous system effects and tachycardia.","Contaminated solutions can cause corneal infections; use single-dose containers when possible."] |
| Food/Dietary | No significant food interactions. Avoid alcohol as it may enhance CNS side effects. |
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| Monitor maternal heart rate and blood pressure for systemic anticholinergic effects. In fetus, monitor heart rate if systemic toxicity suspected. No routine fetal monitoring required. |
| Fertility Effects | No known effects on fertility. Systemic anticholinergic effects at high doses could potentially affect reproductive function, but unlikely with ophthalmic use. |
| Clinical Pearls | Cyclopentolate (Cyclogyl) is a potent anticholinergic cycloplegic and mydriatic. Onset of cycloplegia is 25-75 minutes; recovery may take 1-4 days. Use the lowest effective concentration (0.5% for infants, 1-2% for adults). Systemic absorption can cause CNS effects, especially in children and the elderly. Monitor for signs of anticholinergic toxicity: flushing, dry skin, tachycardia, fever, hallucinations. In patients with narrow angles, cycloplegia can precipitate acute angle-closure glaucoma. Use with caution in patients with Down syndrome, spastic paralysis, or brain damage due to increased sensitivity. |
| Patient Advice | This medication will cause blurred vision and sensitivity to light for up to several days. Wear sunglasses and avoid driving or operating machinery until vision clears. · Do not touch the dropper tip to any surface to avoid contamination. Wash hands before and after instillation. · Apply pressure to the tear duct (inner corner of the eye) for 1-2 minutes after instillation to reduce systemic absorption. · Notify your doctor immediately if you experience eye pain, redness, rapid heartbeat, confusion, or signs of an allergic reaction. · Keep out of reach of children. Overdose can cause severe side effects including flushed skin, fever, hallucinations, and seizures. |