The crystal of mercurous chloride prepared by sublimation.
Appearing as laminal crystals like snowflakes, with silver-white luster,
easily broken into powder when compressed. Tuming to yellow and becoming
smoke when heated on a plate of iron. Acrid in taste, cold in nature,
toxic, and attributive to large and small intestine channels.
1. Clear away toxic material, kill parasite and alleviate itching: For
scabies, tinea, syphilitic lesion, pustulosis, and eczema.
2. Induce diarrhea and relieve edema: For ascites of sthenic type with
dyschesia and dysuria.
1. It is a common preparation of cathartic. A small dose of calomel is
to more soluble mercuric ions which inhibit the activity of sodium and
other ions in the intestines and retain electrolytes and water in the
bowel. This probably interprets the mechanism of the cathartic action
2. Its aqueous solution is an fungicide and applicable to the treatment
of various skin diseases.
Pill or capsule: 0.1-0.2g once or twice daily.
External use: Appropriate amount.
Calomelas is irritative and may cause erosion of oral mucosa. Contraindicated
for pregnant women and those with renal insufficiency. Mercurous chloride
may be converted to mercuric chloride after heated and the toxicity is
increased. Hence, the drug should not be decocted for oral use.