4-(M-Chlorophenylcarbamoyloxy)-2-butynyl)trimethylammonium (McN-A-343) is a selective muscarinic M1 receptors agonist, which leads to its widespread use as an aid to distinguish responses mediated through M₁ receptors from those utilizing M₂ or M₃ muscarinic receptor subtypes, especially in the CNS. McN-A-343 has a number of non-muscarinic actions. These include activation of some types of nicotinic acetylcholine receptors, antagonism of serotonin 5-HT₃ and 5-HT₄ receptor subtypes, inhibition of the uptake mechanism and a local anesthetic action.

Ni acetate is a water soluble salt of Ni, which leads to skin irritation, in particular to allergic contact dermatitis. May cause cancer according to animal studies. Symptoms of overexposure to nickel can cause sensitization, dermatitis, allergic asthma and pneumonitis.