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Antidepressants - Receptor affinities(2)

Date Created: 05/04/1999 Last Modified: 27/12/2002 Last Checked: 27/12/2002

Potency for blocking H1 and (A1) post-synaptic receptors

H1 blockade relates to a) sedation, and b) weight gain
A1 relates to postural hypotension and reflex tachycardia

mirtazapine 0.12 (-)
Doxepin 0.2 (23)
Mianserin 0.4 (34)
Amitriptyline 1 (24)
Dothiepin 3.6 (450)
Nortriptyline 6.3 (55)
Clomipramine 15 (50)
Imipramine 37 (32)
Desipramine 60 (100)
Nefazodone 24000 (48)
trazodone 1100 (42)
Sertraline 24000 (380)
venlafaxine 35000 (35000)

Doxepin and mirtazapine are the most potent antihistamines on the world market, indeed, because of this doxepin has been marketed as a topical skin preparation.

Doxepin and mirtazapine are extremely sedative, being at least two orders of magnitude more potent in this respect than desipramine. Many patients will get a good sedative effect from 10 mg of doxepin; that accords with data indicating that as a sedative 15 mg of mirtazapine is equivalent to 10 mg of diazepam.

The top 5-6 drugs on this list may well be too sedative to be satisfactory for routine use in most circumstances. Note the possible relationship between sedative potency and the risks of road traffic accidents; with amitriptyline this risk appears to be increased about fivefold.

As an A1 blocker desipramine is the least hypotensive (lofepramine is not in the list but is probably very similar (it is metabolised into desipramine anyway).