Chlorphenamine

Chlorphenamine 180px Systematic (IUPAC) name 3-(4-chlorophenyl)-N,N-dimethyl- 3-pyridin-2-yl-propan-1-amine Clinical data Pregnancy category AU: A US: B (No risk in non-human studies) Routes of administration Oral, IV, IM, SC Legal status Legal status AU: S3 (Pharmacist only) UK: General sales list (GSL, OTC) US: OTC (for oral forms) Pharmacokinetic data Bioavailability 25 to 50% Protein binding 72% Metabolism Hepatic (CYP2D6) Biological half-life 21-27 hours Excretion Renal Identifiers CAS Number 132-22-9 ATC code R06AB04 (WHO) PubChem CID 2725 IUPHAR/BPS 1210 DrugBank DB01114 ChemSpider 2624 Chemical data Formula C16H19ClN2 Molar mass 274.788 g/mol[[]] Physical data Solubility in water 0.55 g/100 mL, liquid mg/mL (20 °C)   (verify)

File:DSC000776.JPG Chlorphenamine 4mg, in the UK

Chlorphenamine (chlorpheniramine), commonly marketed in the form of chlorphenamine maleate (Chlor-Trimeton, Piriton, Chlor-Tripolon, HISTA-12), is a first-generation alkylamine antihistamine used in the prevention of the symptoms of allergic conditions such as rhinitis and urticaria. Its sedative effects are relatively weak compared to other first-generation antihistamines. Chlorpheniramine is one of the most commonly used antihistamines in small-animal veterinary practice as well. Although not generally approved as an antidepressant or anti-anxiety medication, chlorpheniramine appears to have these properties as well (see below).

Chlorpheniramine is part of a series of antihistamines including pheniramine (Naphcon) and its halogenated derivatives and others including fluorpheniramine, dexchlorpheniramine (Polaramine), brompheniramine (Dimetapp), dexbrompheniramine (Drixoral), deschlorpheniramine, dipheniramine (also known as triprolidine with the trade name Actifed), and iodopheniramine.

The halogenated alkylamine antihistamines all exhibit optical isomerism, and chlorpheniramine in the indicated products is racemic chlorpheniramine maleate, whereas dexchlorpheniramine (Polaramine) is the dextrorotary stereoisomer.

It is also known as Comakin in Taiwan and parts of Asia.

Serotonergic and norepinephrinergic effects

In addition to being an H-1 histamine receptor antagonist, chlorpheniramine has been shown to work as a serotonin-norepinephrine reuptake inhibitor or SNRI. A similar antihistamine, brompheniramine, led to the discovery of the SSRI zimelidine. Limited clinical evidence shows that it is comparable to several antidepressant medications in its ability to inhibit the reuptake of serotonin and also norepinephrine (noradrenaline). However, extensive clinical trials of its psychiatric properties in humans have not been conducted. It inhibits serotonin reuptake less than norepinephrine reuptake, however the literature is not consistent in this respect (compare Hellbom (2005) with Domino (1999)).

Combination medications

Chlorpheniramine is often combined with phenylpropanolamine to form an allergy medication with both antihistamine and decongestant properties. Brand names include Demazin, Allerest 12 Hour, Codral Nighttime, Chlornade, Contac 12 Hour, A. R. M. Allergy Relief, Ordrine, Ornade Spansules, Teldrin, Triaminic, and Tylenol Cold/Allergy.

Chlorpheniramine is combined with a narcotic (hydrocodone) in the product Tussionex, which is indicated for treatment of cough and upper respiratory symptoms associated with allergy or cold in adults and children 6 years of age and older. This combination is manufactured as a time-released formula, which allows for administration every 12 hours, versus the more common 4-to-6-hour regimen for other narcotic cough suppressants. Chlorpheniramine/Dihydrocodeine immediate-release syrups are also marketed. The antihistamine is helpful in cases where allergy or common cold is the reason for the cough; it is also a potentiator of opioids, allowing enhanced suppression of cough, analgesia, and other effects from a given quantity of the drug by itself. In various places in the world, cough & cold preparations containing codeine and chlorpheniramine are available.

In the drug Coricidin, Chlorphenamine is combined with the cough suppressant dextromethorphan.

See also

• Diphenhydramine
• Dexchlorpheniramine

References

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