Pseudoephedrine

Absorption

A 240mg oral dose of pseudoephedrine reaches a Cmax of 246.3±10.5ng/mL fed and 272.5±13.4ng/mL fasted, with a Tmax of 6.60±1.38h fed and 11.87±0.72h fasted, with an AUC of 6862.0±334.1ng*h/mL fed and 7535.1±333.0ng*h/mL fasted.

Toxicity

The oral LD50 of pseudoephedrine is 2206mg/kg in rats and 726mg/kg in mice.
Patients experiencing an overdose of pseudoephedrine may present with giddiness, headache, nausea, vomiting, sweating, thirst, tachycardia, precordial pain, palpitations, difficulty urinating, muscle weakness, muscle tension, anxiety, restlessness, insomnia, toxic psychosis, cardiac arrhythmias, circulatory collapse, convulsions, coma, and respiratory failure. Treat overdose with symptomatic and supportive treatment including removal of unabsorbed drug.

Description

Pseudoephedrine is a stereoisomer of ephedrine, in the drug class of sympathomimetics. It occurs naturally in plants of the genus Ephedra. Pseudoephedrine is a mixed-acting decongestant, which activates α- and β-adrenergic receptors directly by binding to the receptor itself, and indirectly by causing norepinephrine release in synaptic nerve terminals.
Pseudoephedrine is also used illicitly in the production of methamphetamine. In the United States, two recent acts of legislation – the Combat Methamphetamine Epidemic Act of 2005 and the Methamphetamine Production Prevention Act of 2008– have created stringent regulation on the sale of pseudoephedrine without a prescription. Pseudoephedrine-containing products were moved behind the counter, only to be sold by the pharmacist using their professional judgment and discretion. Limitations on the quantity of pseudoephedrine that could be purchased at one time and over a period of timewere enacted, and strict record keeping was required.

Description

Pseudoephedrine is an over-the-counter medication that has three sides: the good, the bad, and the ugly. It is a diastereomer of ephedrine, meaning that it has the same basic structure, but its atomic arrangement is different at one of the two stereogenic centers. Pseudoephedrine exists as two enantiomers; the one used commercially is the (1S,2S)-form that is shown in the images.
Pseudoephedrine was first known as a natural substance that occurs in shrubs of the?Ephedra?genus, which grow worldwide. Almost all commercial pseudoephedrine, however, is produced by fermenting dextrose in the presence of benzaldehyde. The primary product, (R)-phenylacetylcarbinol, is aminated to make pseudoephedrine.
What does pseudoephedrine do, and what are its downsides?
Some good news: A?recent study?showed that since restrictions went into effect, the use of methamphetamine has declined.

Description

(1S,2S)-(+)-Pseudoephedrine (Item No. 14209) is an analytical reference standard that is categorized as an amphetamine. (1S,2S)-(+)-Pseudoephedrine is a precursor in the synthesis of methamphetamine (Item Nos. 13997 | 13998 | ISO60168). This product is intended for research and forensic applications.

Chemical properties

white crystals

The Uses of Pseudoephedrine

Pseudoephedrine is an orally active sympathomimetic amine that is used as a nasal decongestant. It exerts its decongestant action by acting directly on a-adrenergic receptors in the respiratory tract mucosa producing vasoconstriction resulting in shrinkage of swollen nasal mucous membranes, reduction of tissue hyperemia, edema, and nasal congestion, and an increase in nasal airway patency. Drainage of sinus secretions is increased and obstructed eustachian ostia may be opened. Relaxation of bronchial smooth muscle by stimulation of b-adrenergic receptors may also occur.

Indications

Pseudoephedrine is a sympathomimetic amine used for its decongestant activity.

Background

Pseudoephedrine is structurally related to ephedrine but exerts a weaker effect on the sympathetic nervous system. Both drugs naturally occur in in ephedra plant which have a history of use in traditional Eastern medicine and were first researched in the west in 1889. The decongestant effect of pseudoephedrine was described in dogs in 1927.

Definition

ChEBI: A member of the class of the class of phenylethanolamines that is (1S)-2-(methylamino)-1-phenylethan-1-ol in which the pro-S hydrogen at position 2 is replaced by a methyl group.

brand name

Efidac (ALZA); Novafed (Sanofi Aventis); Sudafed (GlaxoSmithKline); Sudafed (Warner Lambert).

General Description

(Sudafed, Afrinol, Drixoral) isthe (S,S) diastereoisomer of ephedrine. Whereas ephedrinehas a mixed mechanism of action, L-(+)-pseudoephedrineacts mostly by an indirect mechanism and has virtually nodirect activity. The structural basis for this difference inmechanism is the stereochemistry of the carbon atom possessingthe β-OH group. In pseudoephedrine, this carbon atompossesses the (S) configuration, the wrong stereochemistryat this center for a direct-acting effect at adrenoceptors.Although it crosses the BBB (log P=1.05, pKa=9.38),L-(+)-pseudoephedrine’s lack of direct activity affords fewerCNS effects than does ephedrine. It is a naturally occurringalkaloid from the Ephedra species. This agent is found inmany OTC nasal decongestant and cold medications.Although it is less prone to increase blood pressure thanephedrine, it should be used with caution in hypertensiveindividuals, and it should not be used in combination withMAO inhibitors.

Contact allergens

This sympathomimetic a-adrenergic agonist is found in plants of the genus Ephedra (Ephedraceae) and is systemically used as a nasal decongestant. It can induce drug skin reactions such as acute generalized exanthematic pustulosis or generalized eczema.

Pharmacokinetics

Pseudoephedrine causes vasoconstriction which leads to a decongestant effect. It has a short duration of action unless formulated as an extended release product. Patients should be counselled regarding the risk of central nervous system stimulation.

Environmental Fate

Through use as a decongestant and production, release to the environment may result from various waste streams. Pseudoephedrine is also found in plants in the genus Ephedra (Ephedraceae) otherwise known as Ma Huang. It has a vapor pressure of 8.3×104 mm Hg at 25 °C and if released into air it will exist both as vapor and in particulate phase in the atmosphere. Vapor-phase pseudoephedrine will be degraded by reactions with hydroxyl radicals, which are photochemically produced. The half-life for this reaction is estimated at 4 h. Particulate-phase pseudoephedrine will be removed from the atmosphere by wet and dry deposition. Pseudoephedrine is not susceptible to direct photolysis by sunlight.
Based upon an estimated Koc of 73, pseudoephedrine is expected to have a high mobility in soil. The pKa of 10.25 indicates that it will exist primarily in the cation form in the environment and it will absorb more strongly to soil containing clay or organic carbon.

Metabolism

Pseudoephedrine is <1% N-demethylated to an inactive metabolite. The majority of pseudoephedrine is eliminated unmetabolized in the urine.

Purification Methods

Crystallise the amine from dry diethyl ether, or from water and dry it in a vacuum desiccator. [Beilstein 13 IV 1878.]

Toxicity evaluation

Pseudoephedrine is a weak base (pKa, 9.4) that stimulates both α- and β-adrenergic receptors, as well as causing the release of neuronal norepinephrine. This mixed α/β adrenergic stimulation produces both hypertension and tachycardia, as opposed to the hypertension with reflex bradycardia seen with selective a agonists.