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Nordoxepin

Active metabolite of antidepressant drug doxepin

Nordoxepin

Clinical data
Other names	N-Desmethyldoxepin; Desmethyldoxepin; Demethyldoxepin; Monodesmethyldoxepin
Pharmacokinetic data
Elimination half-life	31 hours[1]
Identifiers
IUPAC name (E/Z)-3-(Dibenzo[b,e]oxepin-11(6H)-ylidene)-N-methylpropan-1-amine
CAS Number	1225-56-5 2887-91-4 (hydrochloride) 67035-76-1 ((E)-nordoxepin)) 58534-46-6 ((Z)-nordoxepin)
PubChem CID	4535
ChemSpider	4376
UNII	F498JSH8RR
ChEBI	CHEBI:141547
CompTox Dashboard (EPA)	DTXSID9075406
Chemical and physical data
Formula	C18H19NO
Molar mass	265.356 g·mol−1
3D model (JSmol)	Interactive image
SMILES CNCCC=C1C2=CC=CC=C2COC3=CC=CC=C31
InChI InChI=1S/C18H19NO/c1-19-12-6-10-16-15-8-3-2-7-14(15)13-20-18-11-5-4-9-17(16)18/h2-5,7-11,19H,6,12-13H2,1H3 Key:HVKCEFHNSNZIHO-UHFFFAOYSA-N

Nordoxepin, also known as N-desmethyldoxepin, is an organic compound. A colorless solid, it attracted attention as the major active metabolite of the tricyclic antidepressant (TCA) doxepin (Sinequan).^[2] It has been found to play a significant role in the antidepressant effects of doxepin.^[3]

Nordoxepin is a mixtureof(E) and (Z) stereoisomers.^[2] Whereas pharmaceutical doxepin is supplied in an approximate 85:15 ratio mixture of (E)- and (Z)-stereoisomers and plasma concentrations of doxepin remain roughly the same as this ratio with treatment, plasma levels of the (E)- and (Z)-stereoisomers of nordoxepin, due to stereoselective metabolism of doxepin by cytochrome P450 enzymes, are approximately 1:1.^[2]

Nordoxepin is pharmacologically active similarly to doxepin,^[4] but relative to doxepin, is much more potent and selective as a norepinephrine reuptake inhibitor.^[2][5][6] In general, the demethylated variants of tertiary amine TCAs like doxepin are much more potent inhibitorsofnorepinephrine reuptake, less potent inhibitors of serotonin reuptake, and less potent in their antiadrenergic, antihistamine, and anticholinergic activities.^[5][6][7]

Nordoxepin is formed from doxepin mainly by CYP2C19 (>50% contribution), while CYP1A2 and CYP2C9 are involved to a lesser extent, and CYP2D6 and CYP3A4 are not involved.^[8] Hydroxylation of doxepin and nordoxepin is mediated mainly by CYP2D6.^[3] Total exposures to both doxepin and nordoxepin differ by almost 10-fold in CYP2D6 ultra-rapid versus poor metabolizers.^[3] Both doxepin and nordoxepin are also transformed into glucuronide conjugates.^[3] The elimination half-life of nordoxepin is approximately 31 hours, which is almost twice that of doxepin (mean 17 hours).^[1]

See also[edit]

• Cidoxepin

References[edit]

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