CYCLOMYDRIL
Clinical safety rating: caution
Comprehensive clinical and safety monograph for CYCLOMYDRIL (CYCLOMYDRIL).
Cyclomydril is a combination of cyclopentolate, an anticholinergic agent that blocks muscarinic receptors, causing mydriasis and cycloplegia, and phenylephrine, an alpha-1 adrenergic agonist that induces mydriasis by contracting the dilator muscle of the iris.
| Metabolism | Cyclopentolate is metabolized primarily via hydrolysis; phenylephrine is metabolized by monoamine oxidase (MAO) and catechol-O-methyltransferase (COMT) in the liver and gut wall. |
| Excretion | Primarily renal excretion as unchanged drug and metabolites. Approximately 80% of cyclopentolate is excreted in urine within 24 hours as parent compound and hydrolysis products. Fecal elimination accounts for <5%. |
| Half-life | The terminal elimination half-life of cyclopentolate in adults is approximately 2–5 hours. In children, the half-life may be prolonged due to immature renal function, increasing risk of systemic toxicity. |
| Protein binding | Cyclopentolate is approximately 50% bound to plasma proteins, primarily albumin. |
| Volume of Distribution | After systemic absorption, the apparent volume of distribution is approximately 1–2 L/kg, indicating extensive tissue distribution including penetration into the CNS. |
| Bioavailability | Following topical ophthalmic administration, systemic bioavailability is low but variable (estimated 1–10%) due to drainage through the nasolacrimal duct and absorption from the nasal mucosa and gastrointestinal tract. |
| Onset of Action | Ophthalmic: Mydriasis and cycloplegia begin within 15–30 minutes following topical instillation, with maximal effect at 30–60 minutes. |
| Duration of Action | Mydriasis persists for up to 24 hours, while cycloplegia lasts 6–12 hours. In children, effects may be more prolonged. |
1 to 2 drops of Cyclomydril (0.2% cyclopentolate hydrochloride and 1% phenylephrine hydrochloride) instilled into the conjunctival sac of each eye, repeated as needed for diagnostic procedures, up to a maximum of 4 doses per day.
| Dosage form | SOLUTION/DROPS |
| Renal impairment | No dose adjustment required for renal impairment as systemic absorption is minimal. |
| Liver impairment | No dose adjustment required for hepatic impairment as systemic absorption is minimal. |
| Pediatric use | Infants and children: 1 drop of Cyclomydril (0.2% cyclopentolate and 1% phenylephrine) instilled into each eye 40-50 minutes prior to examination; may repeat once after 10-15 minutes if needed. Maximum 2 drops per eye per procedure. |
| Geriatric use | Use with caution in elderly patients due to increased risk of systemic absorption and adverse effects (e.g., tachycardia, hypertension, confusion). Reduce dose if necessary; avoid prolonged use. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for CYCLOMYDRIL (CYCLOMYDRIL).
| Breastfeeding | Cyclopentolate: minimal systemic absorption; likely compatible. Phenylephrine: excreted in breast milk, M/P ratio unknown; may reduce milk production via vasoconstriction. Use with caution; monitor infant for irritability, tachycardia, hypertension. |
| Teratogenic Risk | Cyclomydril contains cyclopentolate and phenylephrine. Cyclopentolate: FDA Category C. Insufficient human data; animal studies show embryo-fetal toxicity at high doses. Phenylephrine: FDA Category C. Risk of fetal hypoxia due to maternal hypertension; avoid in preeclampsia. First trimester: theoretical risk; second/third trimester: risk of preterm labor, reduced uterine blood flow. Use only if clearly needed. |
■ FDA Black Box Warning
None.
| Serious Effects |
["Narrow-angle glaucoma or anatomically narrow angles","Hypersensitivity to cyclopentolate or phenylephrine","Concurrent use with monoamine oxidase inhibitors (MAOIs) or within 21 days of MAOI discontinuation"]
| Precautions | ["Risk of central nervous system disturbances (e.g., behavioral changes, hallucinations) especially in children","Increased intraocular pressure risk in patients with narrow-angle glaucoma","Cardiovascular effects (e.g., hypertension, arrhythmias) due to phenylephrine","Use cautiously in patients with Down syndrome, brain damage, or spastic paralysis"] |
| Food/Dietary | No significant food interactions. Avoid alcohol in breastfeeding mothers as it may exacerbate side effects in the infant. |
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| Fetal Monitoring | Monitor maternal blood pressure, heart rate, and signs of systemic effects (palpitations, hypertension, tachycardia). Fetal monitoring indicated if maternal hypertension develops. Observe for preterm labor. |
| Fertility Effects | Cyclopentolate: no known effect on fertility. Phenylephrine: high doses may impair uterine blood flow; no direct evidence of fertility impairment. |
| Clinical Pearls | Cyclomydril is a fixed-dose combination of cyclopentolate 0.2% and phenylephrine 1% used for pupillary dilation in premature infants and neonates. The low concentrations minimize systemic anticholinergic and sympathomimetic side effects. Administer 1 drop per eye 15-20 minutes prior to examination; repeat if needed after 10-15 minutes. Avoid use in patients with narrow-angle glaucoma or known hypersensitivity. Monitor for tachycardia, hypertension, flushing, and feeding intolerance post-administration. |
| Patient Advice | Apply the prescribed number of drops into the eye(s) as directed by the healthcare provider. · Do not touch the dropper tip to any surface, including the eye, to avoid contamination. · After instilling the drop, press gently on the inner corner of the eye (nasolacrimal sac) for 1-2 minutes to reduce systemic absorption. · The medication may cause temporary blurred vision and sensitivity to light; protect eyes with sunglasses. · Notify the doctor if the infant experiences fast heartbeat, flushing, fever, or difficulty feeding. · Keep out of reach of children. |