Calcium Calcium Calcium is a chemical element with symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to its heavier homologues strontium and barium. It is the fifth most abundant element in Earth's crust and the third most abundant metal, after iron and aluminium. The most common calcium compound on Earth is calcium carbonate, found in limestone and the fossilised remnants of early sea life; gypsum, anhydrite, fluorite, and apatite are also sources of calcium. The
Calcium channel opener Calcium channel opener A calcium channel opener is a type of drug which facilitates ion transmission through calcium channels. An example is Bay K8644, which is an analogue of nifedipine that specifically and directly activates L-type voltage-dependent calcium channels. In contrast to Bay K8644, which is not for clinical use, Ambroxol is a frequently used mucolytic drug that triggers lysosomal secretion by mobilizing calcium from acidic calcium stores. This effect does most likely not occur by a direct interaction between the drug and a lysosomal calcium channel, but indirectly by neutralizing the acidic pH within lysosomes. Calcium permeable ion channels