Maois
Contraindicated
Database
MAO inhibition prevents phenylephrine metabolism; hypertensive crisis risk
Avoid within 14 days of MAOI use
Source: Kimi deep-research + Cla
Drug reference
Phenylephrine
Alpha-1 adrenergic receptor agonist (sympathomimetic) / decongestant / vasopressor · Decongestant, Vasopressor, Mydriatic
Also known as Phenylephrine Hydrochloride, Neo-Synephrine
START
Nasal: 0.25-1% spray, 2-3 sprays q4h PRN; limit to 3 days max (rebound congestion). Oral: 10 mg q4h PRN. IV: 100 mcg/min, titrate to MAP >65
TYPICAL MAX
Oral: 60 mg/day; Nasal: max 3 days; IV: titrate to effect
STOP IF
Severe hypertension (SBP >180), chest pain, arrhythmias, nasal use >3 days (rebound congestion)
WATCH
BP (systemic use), nasal symptoms (rebound congestion with prolonged use), HR, signs of ischemia
CDSCO approvedSchedule H (for injectable and some higher-strength oral/ophthalmic preparations), otherwise OTC for many lower-strength decongestant nasal sprays and oral formulations.Jan AushadhiATC C01CA06 (vasopressor); R01BA03 (nasal decongestant); S01FB01 (mydriatic)
KDIGO 2024 + manufacturer label
- ONSET
- 15min · Nasal: minutes; Oral: 15-30 min
- PEAK
- 1.5h · Oral: 1-2 hours
- t½
- 2.5h · 2-3 hours
- DURATION
- 5h · 4-6 hours
EXCRETION
Renal (sulfate conjugates)
route + CYP
INTERACTIONS
12 major
incl. contraindicated
PREGNANCY
Avoid in first trimester; use with caution in second/third trimester; may reduce uterine blood flow
FDA category + note
Top interactionssee all 12 →
- MaoisContraindicatedDatabaseKimi deep-research + Cla
- AmitriptylineSevereDatabaseDDInter
- AmoxapineSevereDatabaseDDInter
- ClomipramineSevereDatabaseDDInter
Available in India
11 branded formulations and 147 fixed-dose combinations. Look up specific brands in the Drugs workspace.
Jan Aushadhi — generic available at GoI pharmacies
Mechanism
Direct-acting sympathomimetic amine that selectively stimulates alpha-1 adrenergic receptors on vascular smooth muscle, causing vasoconstriction. When used topically (nasal), this reduces nasal mucosal blood flow and congestion. When used IV, it increases systemic vascular resistance and BP. Minimal beta-adrenergic activity.
Indications
Nasal congestion (topical or oral decongestant)Hypotension / shock (IV vasopressor)Mydriasis (ophthalmic)Hemorrhoids (rectal)Priapism (off-label, intracavernosal)
Dosing
- Adult
- Nasal: 0.25-1% spray, 2-3 sprays per nostril q4h PRN (max 3 days). Oral: 10 mg q4h PRN (max 60 mg/day). IV: 100-180 mcg/min infusion, titrate to BP. Ophthalmic: 1 drop 2.5-10% solution
- Pediatric
- Nasal: >6 years: 0.25% spray 2-3 sprays q4h. <6 years: 0.125% solution. Oral: not recommended <12 years
- Renal adjustment
- No adjustment needed
- Hepatic adjustment
- No adjustment needed
- Geriatric
- Use with caution; increased sensitivity to hypertension and arrhythmias
- Max dose
- Oral: 60 mg/day; Nasal: max 3 days continuous use (rebound congestion)
Pharmacokinetics
Onset
Nasal: minutes; Oral: 15-30 minutes; IV: immediate
Peak effect
Oral: 1-2 hours; IV: immediate
Duration
Nasal: 4-6 hours; Oral: 4-6 hours; IV: 15-20 minutes after stopping
Half-life
2-3 hours
Bioavailability
Oral: ~38% (extensive first-pass metabolism)
Protein binding
Not well characterized
Metabolism
Hepatic MAO (monoamine oxidase) and sulfotransferase (SULT1A3)
Excretion
Renal (primarily as sulfate conjugates)
Contraindications
- Hypersensitivity to phenylephrine
- Severe hypertension
- Severe coronary artery disease
- Narrow-angle glaucoma (systemic use)
- Hyperthyroidism
- Concurrent MAOI use (within 14 days)
- Pheochromocytoma
Side effects
Common
Nasal: burning, stinging, dryness, sneezingSystemic: hypertension, headache, nervousness, dizziness, insomnia, nauseaOphthalmic: transient stinging, blurred vision, photophobia
Serious
- Severe hypertension / hypertensive crisis
- Arrhythmias
- Myocardial ischemia
- Stroke (rare)
- Rebound nasal congestion (rhinitis medicamentosa with >3 days use)
- Severe allergic reactions
Pregnancy & lactation
Pregnancy
Avoid in first trimester; use with caution in second/third trimester; may reduce uterine blood flow
Lactation
Excretion in breast milk unknown; likely minimal with nasal/topical use; use caution with oral/IV forms
Drug interactions
Amitriptyline
Severe
Database
Drug interaction classified as: synergy.
Source: DDInter
Amoxapine
Severe
Database
Drug interaction classified as: synergy
Source: DDInter
Clomipramine
Severe
Database
Drug interaction classified as: synergy
Source: DDInter
Desipramine
Severe
Database
Clinical effect not specified
Source: DDInter
Dihydroergotamine
Severe
Database
Clinical effect not specified
Source: DDInter
Doxepin
Severe
Database
Clinical effect not specified
Source: DDInter
Ergometrine
Severe
Database
Clinical effect not specified
Source: DDInter
Ergotamine Tartrate
Severe
Database
Drug interaction classified as: synergy
Source: DDInter
Halothane
Severe
Database
Clinical effect not specified
Source: DDInter
Imipramine
Severe
Database
Clinical effect not specified
Source: DDInter
Isocarboxazid
Severe
Database
Clinical effect not specified
Source: DDInter
Related guidelines
Ask House about Phenylephrine
Continue into a citation-backed clinical answer with the drug context already attached.
Sources: KD Tripathi 7e, Goodman & Gilman 14e, Katzung, BNF·Verified: 2026-05-19 · House clinical team·Cockpit curated: 2026-05-19