Products
Phenylephrine is commercially available in the form of eye drops (Neosynephrine-POS 5%).
Structure and properties
Phenylephrine(C9H13NO2, Mr = 167.2 g/mol) is a derivative of epinephrine. It exists as phenylephrine hydrochloride, a white crystalline powder that is readily soluble in water. The drug contains the pure -enantiomer.
Effects
Phenylephrine (ATC S01FB01) has mydriatic and vasoconstrictor properties. The effects are due to agonism at α1-adrenoceptors on the inner eye muscles. The effects last for approximately five hours.
Indications
For short-term pupillary dilation in adults for examination of the fundus of the eye.
Dosage
According to the Smear Guide. 1 drop is instilled into the conjunctival sac of the eye being examined. See also under Administering eye drops.
Contraindications
- Hypersensitivity
- Severe cardiovascular changes, e.g., severe congestive heart failure
- Rhinitis sicca
- Narrow-angle glaucoma
- Pregnancy and lactation
- Children and adolescents
For complete precautions, see the drug label.
Interactions
Systemic drug interactions cannot be ruled out. They may occur, for example, with antidepressants and antihypertensives.
Adverse effects
Possible adverse effects include a burning sensation in the eyes. Do not drive for several hours after the examination because phenylephrine causes transient visual disturbances (especially accommodation problems). Systemic side effects such as an increase in blood pressure, on the other hand, are very rare.
