NAPHAZOLINE HYDROCHLORIDE AND PHENIRAMINE MALEATE
Clinical safety rating: caution
Comprehensive clinical and safety monograph for NAPHAZOLINE HYDROCHLORIDE AND PHENIRAMINE MALEATE (NAPHAZOLINE HYDROCHLORIDE AND PHENIRAMINE MALEATE).
Naphazoline is an alpha-adrenergic receptor agonist that causes vasoconstriction of conjunctival blood vessels, reducing redness and edema. Pheniramine is a histamine H1-receptor antagonist that blocks the effects of histamine, reducing itching and allergic symptoms.
| Metabolism | Naphazoline: Primarily hepatic metabolism via monoamine oxidase (MAO); Pheniramine: Hepatic metabolism via cytochrome P450 (CYP) enzymes, including CYP2D6 and CYP3A4. |
| Excretion | Naphazoline: Renal excretion of unchanged drug and metabolites accounts for >80% of elimination. Pheniramine: Renal excretion of unchanged drug and metabolites accounts for >90% of elimination, with <5% biliary/fecal elimination. |
| Half-life | Naphazoline: Terminal elimination half-life approximately 2-3 hours; clinical effects may persist longer due to local vasoconstriction. Pheniramine: Terminal elimination half-life approximately 14-16 hours; appropriate for twice-daily dosing. |
| Protein binding | Naphazoline: Approximately 25% bound to plasma proteins (albumin). Pheniramine: Approximately 70-80% bound to plasma proteins (albumin). |
| Volume of Distribution | Naphazoline: Vd ~1.5 L/kg, indicating moderate distribution into tissues. Pheniramine: Vd ~4-6 L/kg, indicating extensive tissue distribution, including CNS. |
| Bioavailability | Ophthalmic: Low systemic bioavailability due to small dose and local administration; systemic absorption <1% of applied dose. Not intended for systemic use. |
| Onset of Action | Ophthalmic: Onset within 10 minutes (naphazoline vasoconstriction); pheniramine antihistamine effect begins within 15-30 minutes. |
| Duration of Action | Ophthalmic: Duration of vasoconstriction 2-6 hours; antihistamine effect may last 4-6 hours. Clinical use: Twice daily or as needed for relief of ocular itching and redness. |
1-2 drops or sprays in each nostril every 4-6 hours as needed, not to exceed 5-7 days
| Dosage form | SOLUTION/DROPS |
| Renal impairment | No dose adjustment required for topical use; systemic absorption minimal |
| Liver impairment | No dose adjustment required for topical use; systemic absorption minimal |
| Pediatric use | Children under 6 years: not recommended. Children 6-12 years: 1 drop or spray in each nostril every 6-8 hours, not to exceed 3 days |
| Geriatric use | Use with caution; avoid extended use (>3-5 days) due to increased risk of rhinitis medicamentosa and rebound congestion |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for NAPHAZOLINE HYDROCHLORIDE AND PHENIRAMINE MALEATE (NAPHAZOLINE HYDROCHLORIDE AND PHENIRAMINE MALEATE).
| Breastfeeding | Naphazoline: not known if excreted in human milk; likely minimal due to low systemic absorption. Pheniramine: excreted in breast milk; potentially irritates infant. M/P ratio not established. Use with caution; avoid high doses or prolonged use. |
| Teratogenic Risk | Naphazoline is an imidazoline derivative vasoconstrictor; no adequate studies in pregnant women. Topical ocular use may produce systemic absorption, but risk is low with short-term use. Pheniramine is an alkylamine antihistamine; no teratogenic effects reported in animal studies. Avoid during first trimester if possible. Both drugs are FDA Pregnancy Category C. |
■ FDA Black Box Warning
None
| Serious Effects |
["Hypersensitivity to naphazoline, pheniramine, or any component of the formulation","Narrow-angle glaucoma","Use in children under 6 years of age"]
| Precautions | ["Do not exceed recommended dosage or frequency of use","Prolonged use may cause rebound conjunctival hyperemia","Use caution in patients with cardiovascular disease, hypertension, hyperthyroidism, diabetes, or narrow-angle glaucoma","May cause pupillary dilation leading to angle-closure glaucoma in susceptible patients","Do not use in patients with narrow-angle glaucoma","Discontinue if eye pain, vision changes, or persistent redness occurs"] |
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| Fetal Monitoring | Monitor maternal blood pressure and heart rate due to vasoconstrictive effects of naphazoline. Observe for signs of systemic toxicity (e.g., hypertension, tachycardia). Fetal monitoring not routinely required, but consider if maternal toxicity occurs. |
| Fertility Effects | No known effects of naphazoline on fertility. Pheniramine: No reproductive toxicity reported. No clinical data on impact of this combination on fertility. |