Formulary
Phenylephrine hydrochloride: Indications, Dosing, Side Effects and Interactions
Phenylephrine hydrochloride clinical drug profile including indications, dosing, side effects, cautions and interactions.
MedNext Academy | 5 min read
Phenylephrine hydrochloride: Indications, Dosing, Side Effects and Interactions
Phenylephrine hydrochloride clinical drug profile including indications, dosing, side effects, cautions and interactions.
Indications and dose
**Mydriasis**
- **Child** (To The Eye): Apply 1 drop, to be administered before procedure, a drop of proxymetacaine topical anaesthetic may be applied to the eye a few minutes before using phenylephrine to prevent stinging.
- **Adult** (To The Eye): Apply 1 drop, to be administered before procedure, then apply 1 drop after 60 minutes if required, a drop of topical anaesthetic may be applied to the eye a few minutes before using phenylephrine to prevent stinging.
**Acute hypotension**
- **Adult** (By Subcutaneous Injection, Or By Intramuscular Injection): Initially 2-5 mg, followed by 1-10 mg, after at least 15 minutes if required.
- **Adult** (By Slow Intravenous Injection): 100-500 micrograms, repeated as necessary after at least 15 minutes.
- **Adult** (By Intravenous Infusion): Initially up to 180 micrograms/minute, reduced to 30-60 micrograms/minute, adjusted according to response.
**Mydriasis for phenylephrine hydrochloride**
- **Child** (To the eye): Apply 1 drop, to be administered before procedure, a drop of proxymetacaine topical anaesthetic may be applied to the eye a few minutes before using phenylephrine to prevent stinging.
**Acute hypotension for phenylephrine hydrochloride**
- **Child 1-11 years** (By subcutaneous injection, or by intramuscular injection): 100 micrograms/kg every 1-2 hours (max. per dose 5 mg) as required.
- **Child 12-17 years** (By subcutaneous injection, or by intramuscular injection): Initially 2-5 mg (max. per dose 5 mg), followed by 1-10 mg, after at least 15 minutes if required.
- **Child 1-11 years** (By slow intravenous injection): Initially 5-20 micrograms/kg (max. per dose 500 micrograms), repeated as necessary after at least 15 minutes.
- **Child 12-17 years** (By slow intravenous injection): 100-500 micrograms, repeated as necessary after at least 15 minutes.
- **Child 1-15 years** (By intravenous infusion): Initially 100-500 nanograms/kg/minute, adjusted according to response.
- **Child 16-17 years** (By intravenous infusion): Initially up to 180 micrograms/minute, reduced to 30-60 micrograms/minute, adjusted according to response.
Cautions
When used by eye Asthma; cerebral arteriosclerosis (in adults); corneal epithelial damage; darkly pigmented iris is more resistant to pupillary dilatation and caution should be exercised to avoid overdosage; diabetes (avoid eye drops in long standing diabetes); mydriasis can precipitate acute angle-closure glaucoma in a few patients, usually over 60 years and hypermetropic (long-sighted), who are pre-disposed to the condition because of a shallow anterior chamber (in adults); mydriasis can precipitate acute angle-closure glaucoma in the very few children who are predisposed to the condition because of a shallow anterior chamber (in children); ocular hyperaemia; susceptibility to angle-closure glaucoma With systemic use Coronary disease; coronary vascular thrombosis; diabetes; elderly (in adults); extravasation at injection site may cause necrosis; following myocardial infarction; hypercapnia; hyperthyroidism; hypoxia; mesenteric vascular thrombosis; peripheral vascular thrombosis; Prinzmetal's variant angina; susceptibility to angle-closure glaucoma; uncorrected hypovolaemia Cautions, further information Hypertensive response With systemic use: Phenylephrine has a longer duration of action than noradrenaline (norepinephrine), and an excessive vasopressor response may cause a prolonged rise in blood pressure.
Contraindications
General contra-indications: Hypertension Specific contra-indications: When used by eye 10% strength eye drops in children (in children); 10% strength eye drops in elderly (in adults); aneurysms; cardiovascular disease; thyrotoxicosis With systemic use Severe hyperthyroidism
Side effects
General side-effects: Frequency not known Arrhythmias; palpitations Specific side-effects: Frequency not known When used by eye (topical) Conjunctivitis allergic; eye discomfort; hypertension; myocardial infarction (usually after use of 10% strength in patients with pre-existing cardiovascular disease); periorbital pallor (in children); vision disorders With intracavernosal use Angle closure glaucoma (in adults); anxiety (in adults); appetite decreased (in adults); asthenia (in adults); confusion (in adults); dyspnoea (in adults); headache (in adults); hypertension (in adults); hypoxia (in adults); insomnia (in adults); nausea (in adults); peripheral ischaemia (in adults); psychosis (in adults); tremor (in adults); urinary retention (in adults); vomiting (in adults) With parenteral use Anxiety; cardiac arrest; confusion; dizziness; dyspnoea; extravasation necrosis; flushing; glaucoma exacerbated; glucose tolerance impaired; headache; hyperhidrosis; hypersalivation; hypertensive crisis; hypotension; insomnia; intracranial haemorrhage; ischaemic heart disease; metabolic change; muscle weakness; mydriasis; nausea; pallor; paraesthesia; peripheral coldness; piloerection; psychotic disorder; pulmonary oedema; soft tissue necrosis; syncope; tremor; urinary disorders; vomiting
Interactions
**Severe interactions:**
- The anticoagulant effect of warfarin and other coumarins may be enhanced by prolonged regular use of paracetamol with increased risk of bleeding; occasional doses have no significant effect.
- Ergot alkaloids (ergotamine and methylsergide) Increased risk of ergotism Digoxin and cardiac glycosides Increase the risk of irregular heartbeat or heart attack Warfarin and other coumarins The...
**Other interactions (7):**
- The hepato-toxicity of paracetamol may be potentiated by excessive intake of alcohol.
- The speed of absorption of paracetamol may be increased by metoclopramide or domperidone and absorption reduced by colestyramine.
- Pharmacological interactions involving paracetamol with a number of other drugs have been reported.
- Caution should be taken when paracetamol is used concomitantly with flucloxacillin as concurrent intake has been associated with high anion gap metabolic acidosis due to pyroglutamic acidosis,...
- Phenylephrine should be used with caution in combination with the following drugs as interactions have been reported: Monoamine oxidase inhibitors (including moclobemide) Hypertensive interactions...
- Beta-blockers and other antihypertensives (including debrisoquine, guanethidine, reserpine, methyldopa) Phenylephrine may reduce the efficacy of beta-blocking drugs and antihypertensive drugs.
Pregnancy
When used by eye: Use only if potential benefit outweighs risk. With systemic use: Avoid if possible; malformations reported following use in first trimester; fetal hypoxia and bradycardia reported in late pregnancy and labour.
Breast feeding
When used by eye: Use only if potential benefit outweighs risk-no information available.
Medicinal forms
Solution,Solution,Drops
Clinical governance
**Author:** MedNext Clinical Team. **Clinical reviewer:** Dr Shameer Deen, MBBS, MS, MRCS. **Sources:** BNF, Indian Pharmacopoeia, CIMS India. **Correction:** Report errors at support@mednext.academy.
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