Pseudoephedrine

(1S,2S)-2-(methylamino)-1-phenylpropan-1-ol

Overview

Pseudoephedrine belongs to Stimulants.

Key safety note: Pseudoephedrine can cause insomnia, restlessness, palpitations, raised blood pressure and headache.[3][2][5][7]
Effects
Subjective effects vary. What a substance feels like depends on dose, individual physiology, mindset, and setting. The points below describe commonly reported effects, not guaranteed, uniform, or desirable outcomes.
  • As a decongestant it clears nasal and sinus congestion. Users often notice mild alertness or a slight stimulant 'lift' from the noradrenaline release.
  • Common or higher-dose effects include insomnia, restlessness, nervousness, palpitations, raised heart rate and blood pressure, and occasionally headache or difficulty passing urine.
  • It is a much milder central stimulant than ephedrine or amphetamine and has low intrinsic abuse potential. Its main illicit significance is as a methamphetamine precursor.
Dosing & duration
Harm-reduction note: These are commonly cited reference ranges, not a recommendation or a “safe” dose. Potency, purity, body chemistry, tolerance, and drug combinations vary widely. Start low, go slow, wait for full effects before redosing, and never assume an unknown product matches these figures. Missing data is not evidence of safety.

Oral (tablets, capsules or liquid, immediate- and extended-release formulations).. Pseudoephedrine is an over-the-counter decongestant, not a recreational drug. It is only a weak stimulant. The figures below are standard therapeutic doses. Cardiovascular effects (raised heart rate and blood pressure) and insomnia increase at higher doses. It should be avoided in uncontrolled hypertension or heart disease and never combined with MAO inhibitors. Note that pseudoephedrine is a controlled methamphetamine precursor, so retail sales are quantity-limited and kept behind the pharmacy counter.

Dose ranges

Adult (immediate-release)

60 mg every 4–6 h

Extended-release

120 mg every 12 h, or 240 mg once daily

Maximum

240 mg/day

Duration

onset

≈30 minutes

total

Immediate-release ≈4–6 h, extended-release up to 12–24 h

after effects

Possible insomnia or restlessness

Chemical & Physical Properties
FormulaC10H15NO
Molar mass165.23 g/mol
StateSolid (crystalline)
Melting point118–120 °C
Boiling pointNot reported
DensityNot reported
Vapor pressureNot reported
pKa10.3 (0 °C, amine)
LogP0.89
SolubilitySparingly soluble in water. Freely soluble in alcohol or ether, Very soluble in benzene
Refractive indexNot reported
Identifiers & Synonyms
CAS90-82-4
CAS (enantiomer)
PubChem CID7028
InChIKeyKWGRBVOPPLSCSI-WCBMZHEXSA-N
InChIInChI=1S/C10H15NO/c1-8(11-2)10(12)9-6-4-3-5-7-9/h3-8,10-12H,1-2H3/t8-,10+/m0/s1
SMILESCN[C@@H](C)[C@@H](O)c1ccccc1

Synonyms

  • Sudafed
  • (+)-pseudoephedrine
  • (1S,2S)-(+)-pseudoephedrine
Pharmacodynamics & Biochemistry

Pseudoephedrine is a sympathomimetic amine and the (1S,2S)-(+)-diastereomer of ephedrine, used mainly as an oral nasal decongestant (Sudafed): it constricts the dilated blood vessels of the swollen nasal mucosa through α-adrenergic stimulation, relieving congestion. Like ephedrine it is a mixed-acting sympathomimetic, but predominantly INDIRECT. A comprehensive transporter/receptorome screen found that ephedrine-type compounds act mainly as substrates of the noradrenaline transporter (NET), promoting noradrenaline release, with only weak α2-adrenergic and 5-HT7 binding (Ki 1–10 µM) and no significant β- or α1-adrenergic activity. Pseudoephedrine is a weak releaser: its noradrenaline-release potency (EC50 ≈224 nM) is roughly 4–5× lower than ephedrine's (≈43–72 nM), with even weaker dopamine release and negligible serotonin release: consistent with its milder central-stimulant effect (values below). Because its direct receptor affinities are weak, its decongestant and adverse effects: vasoconstriction, and at higher doses raised heart rate and blood pressure, insomnia and restlessness: are driven largely by the noradrenaline it releases rather than by direct receptor agonism. Pseudoephedrine is eliminated largely unchanged in the urine, and its half-life is strongly pH-dependent, acidic urine shortens it markedly, so urinary pH influences both its duration and its effect.

Biological targets

  • NET
  • Adrenergic system

Binding & functional measurements

TargetMeasurementSpecies
Norepinephrine transporterpEC50 6.65Rat (brain synaptosomes)
Dopamine transporterpEC50 5.7Rat (brain synaptosomes)
Pharmacokinetics
BioavailabilityOral, well absorbed (high oral bioavailability)
Tmax≈1–3 h
Half-life≈5–8 h (markedly shorter in acidic urine)
VdNot reported
Protein bindingNot reported
MetabolismLimited hepatic metabolism
ExcretionLargely renal, excreted unchanged (pH-dependent)
Toxicology & Safety
Harm-reduction note: Toxicity and risk depend on dose, route, purity, combinations, setting, and individual health factors. Missing harms should never be interpreted as evidence of safety.

Not reported

Pseudoephedrine can cause insomnia, restlessness, palpitations, raised blood pressure and headache. It must not be used with MAO inhibitors. European safety measures advise against use in severe or uncontrolled hypertension or severe acute or chronic kidney disease or renal failure because of the risk of posterior reversible encephalopathy syndrome (PRES) and reversible cerebral vasoconstriction syndrome (RCVS). Stop taking it and seek urgent medical assistance for sudden severe headache, vomiting, confusion, seizures or visual changes. Retail restrictions also apply because it can be diverted as a methamphetamine precursor.[3][2][5][7]

Legal Status
Legal note: Legal status can change over time and may vary by country, region, formulation, analogue status, prescription context, and enforcement practice. Always confirm with current official sources before relying on this section.
Interactions & Contraindications

Drug interactions

MAOIs Risk of hypertensive crisis, must not be used with or within two weeks of an MAOI.[3]
Stimulants (amphetamines, cocaine), Caffeine Additive cardiovascular stimulation, including caffeine and other decongestants.[3]
Antihypertensive drugs, Non-selective beta-blockers Pseudoephedrine can blunt their effect and raise blood pressure (beta-blockers, methyldopa).[3]
Urinary acidifiers or alkalinisers Alkalinising the urine prolongs its action, acidifying shortens it.[3]

Contraindications

Cardiovascular disease, hypertension or arrhythmia severe or uncontrolled hypertension and severe coronary artery disease.[3]
Concurrent MAOI, SSRI/SNRI or other serotonergic medication concurrent or recent (within 14 days) MAOI use (hypertensive-crisis risk).[3]
Closed-angle glaucoma closed-angle, and urinary retention (e.g. prostatic enlargement).[3]
Hyperthyroidism also use caution in diabetes and cardiovascular disease.[3]
Kidney or liver impairment severe acute or chronic kidney disease or renal failure (PRES/RCVS risk).[7]
Usage & Context
  • A standard over-the-counter oral decongestant (Sudafed and many combination cold/flu products) for nasal and sinus congestion, and for Eustachian-tube/ear congestion.
  • Its main non-medical significance is as a methamphetamine precursor, which is why its sale is restricted and monitored worldwide. Direct recreational use is limited by its weak stimulant effect.
Sources & Evidence

Further Information