Clemastine

Clemastine

Clinical data
AHFS/Drugs.com	Monograph
MedlinePlus	a682542
Pregnancy category	US: B (No risk in non-human studies)
Routes of administration	Oral
ATC code	D04AA14 (WHO) R06AA04 (WHO)
Legal status
Legal status	In general: Over-the-counter (OTC)
Pharmacokinetic data
Bioavailability	39.2%
Metabolism	Hepatic
Biological half-life	21.3 hours
Excretion	Renal
Identifiers
IUPAC name (2R)-2-{2-[(1R)-1-(4-chlorophenyl)-1-phenylethoxy]ethyl}-1-methylpyrrolidine
CAS Number	15686-51-8 Y
PubChem CID	26987
IUPHAR/BPS	6063
DrugBank	DB00283 Y
ChemSpider	25129 Y
UNII	95QN29S1ID
KEGG	D03535 Y
ChEBI	CHEBI:3738 Y
ChEMBL	CHEMBL1626 Y
Chemical and physical data
Formula	C21H26ClNO
Molar mass	343.9 g/mol
3D model (Jmol)	Interactive image
SMILES Clc1ccc(cc1)[C@](OCC[C@@H]2N(C)CCC2)(c3ccccc3)C
InChI InChI=1S/C21H26ClNO/c1-21(17-7-4-3-5-8-17,18-10-12-19(22)13-11-18)24-16-14-20-9-6-15-23(20)2/h3-5,7-8,10-13,20H,6,9,14-16H2,1-2H3/t20-,21-/m1/s1 Y Key:YNNUSGIPVFPVBX-NHCUHLMSSA-N Y

Clemastine, also known as meclastin, is an antihistamine and anticholinergic. Unlike loratadine or fexofenadine, clemastine is a sedating antihistamine; however, it exhibits fewer other side effects than most of the widely used antihistamines. Clemastine is also classified as an antipruritic (i.e., it stops itching).

Clemastine is indicated for use in treating allergic rhinitis, such as sneezing, rhinorrhea, pruritus and lacrimation.

Overdosage symptoms are paradoxical, ranging from CNS depression to stimulation. Stimulation is most common in children, and is usually followed by excitement, hallucinations, ataxia, loss of coordination, muscle twitching, athetosis, hyperthermia, cyanosis, convulsions, tremors, and hyperreflexia. This may be followed by postictal depression and cardiovascular/respiratory arrest. Other common overdose symptoms include dry mouth, fixed dilated pupils, flushing of the face, and pyrexia. In adults, overdose usually leads to CNS depression, ranging from drowsiness to coma.

Clemastine is an antihistamine with anticholinergic and sedative effects. Antihistamines competitively bind to histamine receptor sites, thus reducing the neurotransmitter's effects. Effects of histamine (which are countered by antihistamines) include: