HY lecture notes:
First-line Tx for diabetic neuropathic pain? –> TCAs (i.e., amitriptyline, nortriptyline).
Important side-effects of TCAs? –> CCC (Coma, Convulsions, Cardiotoxicity) + anti-“triad”: anti-cholinergic + anti-alpha-1-adrenergic + anti-H1-histaminergic effects. (Don’t worry, I’ll explain below).
Anti-“triad” is seen with TCAs, anti-psychotics (classically atypicals [second generation]) and first-generation H1-blockers.
Psych patient is started on new drug + gets prolongation of QT-interval; next best step? –> stop the TCA –> on one of the psych forms, the TCA was doxepin, which is quite strange since this drug is LY to the point that it’s essentially unheard of, but this is the one mentioned on one of the forms.
By anti-cholinergic effects, what are we referring to? –> “opposite of DUMBBELSS” –> DUMBBELSS is the pneumonic for cholinergic effects –> Diarrhea, Urination, Myosis, Bradycardia, Bronchoconstriction, Excitation (neuromuscular), Lacrimation, Salivation, Sweating –> so TCAs can cause the opposite effects due to anti-cholinergic side-effects –> Constipation, Urinary retention, Mydriasis, Tachycardia, (not bronchodilaton), (not muscular relaxation), Xerophthalmia, Xerostomia, Anhydrosis.
The anti-cholinergic side-effects of TCAs, 2nd gen anti-psychotics, or 1st-gen H1-blockers in elderly exacerbate cognitive decline and more readily precipitate delirium.
If the Q tells you someone on a TCA has confusion or disorientiation, it’s alluding to delirium and the answer is discontinue the TCA.
43F + suprapubic mass + hot, dry, red skin on face + started on new drug for depression; which drug was she started on? –> TCA (urinary retention + anhydrosis leading to heat retention).
By anti-alpha-1-adrenergic effects, this refers to orthostatic hypotension + fainting.
We don’t want to give TCAs, 2nd gen anti-psychotics, or 1st-gen H1-blockers to elderly because they can precipitate FALLS.
By anti-H1-histaminergic, this refers to sedation.
If we must give a TCA to an elderly patient, it’s almost always nortriptyline. Apparently this doesn’t penetrate the BBB to the same extent, so the side-effects are not as pronounced as with other TCAs.
There’s a Q on one of the FM forms where they tell you an 82M with diabetes is being treated with carbamazepine + gabapentin for neuropathic pain to no avail; then they ask for the next best step; answer is give nortriptyline.
Another Q gives a 42M with diabetic neuropathic pain, and the answer was simply amitriptyline.
Tx for TCA toxicity? –> sodium bicarb –> dissociates drug from myocardial sodium channels –> sodium as the cation will outcompete the TCA for its own channel + the alkalinization of the serum causes decreased affinity of the TCA for the channel.
Gabapentin is first-line for neuropathic pain associated with herpetic/post-herpetic neuralgia + injury + idiopathic. But for diabetes it’s TCAs.
Carbamazepine is first-line for trigeminal neuralgia.
