Mechanism of action: Nortriptyline balliculeVisual mnemonic: Nortriptyline mascot “North-tripping Pam”
What it isNorepinephrine-predominant tricyclic reuptake inhibitor; depression and neuropathic pain.
Why it mattersThe best-tolerated tricyclic — less anticholinergic and less orthostatic than amitriptyline, and it has a defined therapeutic level range.
What it changesStill lethal in overdose from sodium channel blockade. CYP2D6 substrate; it is the active metabolite of amitriptyline.
Defining liabilityAnticholinergic effects and cardiac sodium-channel blockade make overdose rapidly life-threatening.
Serotonicity
This drug is routinely called serotonergic. By Gillman’s human-effect criteria it does not raise serotonin in the synapse.
Potent NRI with negligible SRI activity; no Gillman-type serotonin-toxicity mechanism.
Label contraindicationMAOIs (concurrently or within 14 days) due to risk of serotonin syndrome. The label governs prescribing; Gillman’s point concerns serotonin toxicity only.
It binds the serotonin transporter, and its SERT peg is drawn to that textbook affinity. The pale halo around the peg marks binding that, by Gillman’s human-effect criteria, does not produce clinical serotonin reuptake inhibition.
Gillman’s four human testsA measurable SERT affinity that fails all four is not clinical serotonicity.