This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.N.S, Subject name: Pharmacology
Tricyclic antidepressants 
Select and explain. 
A. increase the antihypertensive effect of guanethidine, B. have anticonvulsant activity, C. should not be used in patients with glaucoma, D. may increase oral absorption of levodopa
C: should not be used in patients with glaucoma
Answer: C: should not be used in patients with glaucoma 
Explanation: In addition to blocking reuptake of NE and 5HT, pharmacodynamic actions of the tricyclic antidepressants include block of peripheral adrenergic and muscarinic receptors--the former resulting in postural hypotension and the latter, via mydriasis, exacerbating glaucoma. TCAs block the uptake of guanethidine into sympathetic nerve endings, decreasing its antihypertensive effects, and they may cause arrhythmias in overdose. They have no effect on the absorption of levodopa.