Phenylephrine Injection is indicated in adults and children for the treatment of hypotensive states e.g. circulatory failure, during spinal anaesthesia or drug induced hypotension.

Posology

Adults

Phenylephrine Injection may be administered subcutaneously or intramuscularly in a dosage of 2 to 5 mg with further doses of 1 to 10 mg if necessary according to response, or in a dose of 100 to 500 micrograms by slow intravenous injection as a 0.1% solution, repeated as necessary after at least 15 minutes.

Alternatively, 10 mg in 500 ml of glucose 5% injection or sodium chloride 0.9% injection may be infused intravenously, initially at a rate of up to 180 micrograms per minute, reduced according to response to 30-60 micrograms per minute.

Elderly

There is no need for dosage reduction in the elderly.

Paediatric population

100 mcg/kg body weight subcutaneously or intramuscularly.

Method of administration

For subcutaneous, intramuscular, slow intravenous injection or intravenous infusion.

Hypersensitivity to the active substance or to any of the excipients listed in section 6.1.

Patients taking monoamine oxidase inhibitors, or within 14 days of ceasing such treatment.

Severe hypertension and hyperthyroidism.

Avoid in patients with prostatic enlargement.

Great care should be exercised in administering Phenylephrine Injection to patients with pre-existing cardiovascular disease such as ischaemic heart disease, arrhythmias, occlusive vascular disease including arteriosclerosis, hypertension or aneurysms. Anginal pain may be precipitated in patients with angina pectoris.

Care is also required when given to patients with diabetes mellitus.

Phenylephrine is not recommended in subjects with a shallow anterior chamber or a history of acute narrow angle glaucoma. Use of Phenylephrine 10 mg/ml Injection in patients with shallow anterior chamber, a history of acute narrow angle glaucoma and/or insufficient pupil dilation can increase the risk of both iridocele and floppy iris syndrome.

Keep all medicines out of the reach of children.

This medicine contains less than 1 mmol sodium (23 mg) per ml, that is to say essentially 'sodium-free'.

Phenylephrine may interact with cyclopropane and halothane and other halogenated inhalational anaesthetics, to induce ventricular fibrillation. An increased risk of arrhythmias may also occur if phenylephrine injection is given to patients receiving cardiac glycosides, quinidine or tricyclic antidepressants.

Phenylephrine is a hypertensive agent and may consequently reverse the action of many antihypertensive drugs. Interactions of phenylephrine with alpha and beta receptor blocking drugs may be complex.

Drugs which have an effect on α ₁ adrenoceptors could potentiate (such as clonidine) or inhibit (such as doxazosin) the vasopressive action of phenylephrine.

Caution should be applied when administering atomoxetine concurrently, as there is potential for synergistic pharmacological effects.

Severe hypertension may occur following the use of phenylephrine and atropine or other antimuscarinics.

The pressor effects of phenylephrine may be slightly reduced by lithium carbonate.

The effects of phenylephrine may be potentiated by the use of monoamine oxidase inhibitors or reversible inhibitors of monoamine oxidase.

Pregnancy

The safety of phenylephrine during pregnancy has not been established. Due to the vasoconstrictive properties of phenylephrine, the product should be used with caution in patients with a history of pre-eclampsia. Administration of phenylephrine in late pregnancy or labour may cause foetal hypoxia and bradycardia.

Breast-feeding

The safety of phenylephrine during lactation has not been established. Excretion of phenylephrine in breast milk appears to be minimal.

Fertility

No data available

No adverse effects known.

A tabulated list of undesirable effects is outlined below:

The undesirable effects are listed according to organ systems and following frequency:

Not known (cannot be estimated from the available data)

Phenylephrine is without significant stimulating effects on the central nervous system at usual doses.

Reporting of suspected adverse reactions

Reporting suspected adverse reactions after authorisation of the medicinal product is important. It allows continued monitoring of the benefit/risk balance of the medicinal product. Healthcare professionals are asked to report any suspected adverse reactions via the Yellow Card Scheme Website: www.mhra.gov.uk/yellowcard or search for MHRA Yellow Card in the Google Play or Apple App Store.

Symptoms

Symptoms of overdosage include headache, vomiting, hypertension and reflex bradycardia and other cardiac arrhythmias. In severe cases confusion, hallucinations and seizures may occur.

Management

Treatment should consist of symptomatic and supportive measures. The hypertensive effects may be treated with an alpha adrenoreceptor blocking drug, such as phentolamine, 5 to 60 mg i.v. over 10-30 minutes, repeated as necessary.

Pharmacotherapeutic group: adrenergic and dopaminergic agent, ATC code: C01CA

Phenylephrine hydrochloride is a sympathomimetic agent with mainly direct effects on adrenergic receptors. It has predominantly alpha-adrenergic activity and is without significant stimulating effects on the central nervous system at usual doses.

Mechanism of action

After injection it produces peripheral vasoconstriction and increased arterial pressure; it also causes reflex bradycardia.

When injected subcutaneously or intramuscularly, phenylephrine takes 10 to 15 minutes to act. Subcutaneous and intramuscular injections are effective for up to about one and up to about two hours respectively. Intravenous injections are effective for up to about 20 minutes.

Biotransformation

Phenylephrine is metabolised in the liver by monoamine oxidase.

Elimination

The metabolites, their route and rate of excretion have not been identified.

Phenylephrine has been used to induce cardiac myocyte hypertrophy in cultures of rat neonatal mycocytes at doses of 100 µ M and 10 µ M. To the best of our knowledge there have been no human studies associating therapeutic phenylephrine use with the development of cardiac myocyte hypertrophy

Sodium Hydroxide solution 1N

Hydrochloric Acid 36% 1N

Water for injections

Phenylephrine Injection has been stated to be incompatible with alkalies, ferric salts, phenytoin sodium and oxidising agents.

2 years.

Store at 2-25° C. Protect from light

1 ml neutral glass ampoule with red imprint break ring.

Pack size: 6 x 1ml and 10 x 1ml ampoules

Not all pack sizes may be marketed.

No special requirements.