Interactions can be expected between cannabis and a wide range of drugs.
Nortriptyline is a tricyclic antidepressant. Cannabis interacts
adversely with tricyclic andidepressants. Cannabis, on its own, produces
tachycardia as a side-effect. Tricyclics do the same. Combined, there
is an additive effect, with a bigger increase in heart rate. I have seen
this with cannabis + doxepin (heart rate >150, as well as BP 99/75,
dizziness and severe anxiety). In this case, doxepin's hypotensive
(blood pressure-lowering) effect (another common side-effect of
tricyclics) was also potentiated. Tricyclic antidepressants have a
certain effect on the heart. This effect can be described as
cardiotoxicity. In normal dosage, in individuals with no heart disorder,
this causes no problems at all. (In overdosage, tricyclics can produce
serious cardiac arrhythmias.) I suspect that in the interaction with
cannabis, the cardiotoxic effect of tricyclics is somewhat potentiated.
(I don't know if this has produced hazardous changes in ECG rhythm.) The
effects of cannabis + nortriptyline in particular have been documented.
I remember seeing a couple of references to all of this in Martindale's
"Extra Pharmacopoeia," 29th edition, under 'Cannabis,' but I haven't read
The Sputnik THC & Health Pages.
The Sputnik Drug Information Zone