Potassium cyanide is a potent inhibitor of cellular respiration, acting on mitochondrial cytochrome coxidase, hence blocking oxidative phosphorylation. This prevents the body from oxidizing food to produce useful energy. Lactic acidosis then occurs as a consequence of anaerobic metabolism. Initially, acute cyanide poisoning causes a red or ruddy complexion in the victim because the tissues are not able to use the oxygen in the blood. The effects of potassium and sodium cyanide are identical. The person loses consciousness, and death eventually follows over a period of time. During this period, convulsions may occur. Death occurs by hypoxia of neural tissue.

Mercury(II) chloride or mercuric chloride (archaically, corrosive sublimate) is the chemical compound of mercury and chlorine with the formula HgCl 2. This white crystalline solid is a laboratory reagent and a molecular compound. Once used as a treatment for syphilis, it is no longer used for medicinal purposes because of mercury toxicity and the availability of superior treatments. Mercuric chloride is highly toxic, both acutely and as a cumulative poison.

Methanol has a high toxicity in humans. If as little as 10 mL of pure methanol is ingested, for example, it can break down into formic acid, which can cause permanent blindness by destruction of the optic nerve, and 30 mL is potentially fatal, [15] although the median lethal dose is typically 100 mL (3.4 fl oz) (i.e. 1– 2 mL/kg body weight of pure methanol [16] ). Reference dose for methanol is 2 mg/kg/day. [17] Toxic effects take hours to start, and effective antidotes can often prevent permanent damage. [15] Because of its similarities in both appearance and odor to ethanol (the alcohol in beverages), it is difficult to differentiate between the two (such is also the case with denatured alcohol). However, there are cases of methanol resistance, such as that of Mike Malloy, who was the victim of a failed murder attempt by methanol in the early 1930s.

The toxicity of ammonia solutions does not usually cause problems for humans and other mammals, as a specific mechanism exists to prevent its build-up in the bloodstream. Ammonia is converted to carbamoyl phosphate by the enzyme carbamoyl phosphate synthetase, and then enters the urea cycle to be either incorporated into amino acids or excreted in the urine. Fish and amphibians lack this mechanism, as they can usually eliminate ammonia from their bodies by direct excretion. Ammonia even at dilute concentrations is highly toxic to aquatic animals, and for this reason it is classified as dangerous for the environment.