Phenylephrine
What is Phenylephrine for?
Phenylephrine is a vasoconstrictor which can constrict your blood vessels to decrease swelling and therefore can be used as a decongestant. It can be used to treat nasal congestion in cold, flu or allergies, and mydriasis (dilation of the eye pupils).
Phenylephrine is usually combined with painkillers like Paracetamol and antihistamines like Chlorpheniramine in many cold and cough medicines.
How to use it?
Phenylephrine can be taken by mouth or applied to eyes or nose. The dosages for different uses, routes and age groups are listed below:
For nasal congestion
By mouth
Adult
10 mg every 4 hours as needed for at most 7 days.
The maximum daily dose is 60 mg.
Apply to the nose
Adult
Instill 0.25-1% nasal drops or spray into nostrils every 4 hours if necessary.
Child 2-6 years
Instill 2-3 drops 0.125% or 0.16% nasal drops into nostrils every 4 hours if necessary.
Child 6-12 years
Instill 2-3 drops or 1-2 sprays 0.25% solution nasal drops or spray into nostrils every 4 hours if necessary.
For mydriasis (dilation of the eye pupils)
Apply to the eyes
Adult
Instill 1 drop 10% Phenylephrine hydrochloride or less to the eyes. You may repeat in 10-60 minutes if necessary. An anaesthetic should be instilled into the eyes a few minutes before instilling Phenylephrine to avoid irritation.
What are the side effects of Phenylephrine?
Common side effects of Phenylephrine include stomach upset, dizziness, headache, tremors, trouble sleeping and nervousness.
Who should not take Phenylephrine ?
- People allergic to Phenylephrine or any other formulation components.
- Patients with severe hypertension.
- Patients with narrow angle glaucoma.
Pharmacist Tips:
- If using eye drops, do not wear contact lenses during that period.
- Both the nasal and eye drops form of the product may cause transient discomfort, such as burning or stinging, when administered.
- Do not use Phenylephrine for longer than 7-10 days to prevent rebound nasal congestion.
Common dosing schedule:
- N/A
This schedule is for reference only, adjustments may be made according to individual needs.
Some common medications Phenylephrine may interact with:
- Ergot derivatives, e.g. Ergotamine
- Fentanyl
- Monoamine oxidase inhibitors, e.g. Isocarboxazid, Selegiline
- Tricyclic antidepressants, e.g. Amitriptyline, Nortriptyline
Please notify your doctor or pharmacist if you are taking the above medication, dosage adjustments might be needed.
Where to buy Phenylephrine in Hong Kong?
In Hong Kong, Phenylephrine is an over-the-counter medicine which can be purchased without a prescription from any retail outlet in Hong Kong. This includes grocery stores, convenience stores, medicine shops, and pharmacies. It can also be obtained from doctors. To find a pharmacy near you, refer to the list of pharmacies (“Authorized Sellers of Poisons”) from the Hong Kong Department of Health.
For more information about drug names and ingredients, you can visit Hong Kong’s Drug Office at https://www.drugoffice.gov.hk
Need more information?
For detailed information about the use of Phenylephrine in children, pregnancy and breastfeeding, and for questions about drug interactions, please check with your pharmacist or doctor.
Disclaimer: our goal is to provide you with the most relevant drug information and common dosage for Hong Kong. This information does not constitute medical advice. For specific treatment recommendations and advice, always discuss with your doctor or pharmacist, and follow the instructions included with your specific medicine.