Magnesium

Indications: Hypomagnesemia, constipation, arrhythmia, eclampsia, yasthma, ymyocardial infarction. Pharmacology Magnesium is the second most abundant intracellular ion after potassium. It is involved in numerous enzymatic reactions and is a co-factor for many biological processes, most of which use ATP. It is important for bone mineralization, muscular relaxation and neurotransmission. About half of the total body magnesium is in soft tissue, the other half in bone, with less than 1% present in blood.1-3 Intracellular magnesium is mostly bound to ribosomes, phospholipids and nucleotides.1 The estimated average requirement for magnesium in adults isw265mg for females andw350mg/24h for males.4 However, magnesium intake is falling as the use of processed and fast-foods increases, and about half of the US population does not meet this requirement.3,5 Thus, the incidence of chronic magnesium deficiency is probably increasing, with possible health implications, but is unrecognized because of the diagnostic limitations of serum magnesium (see below).3,5 Magnesium competes with calcium for absorption in the small intestine, probably by active transport. The normal serum magnesium is 1.5e1.91mEq/L. However, some have argued that for optimal health, the lower limit for serum magnesium should be considered to be 1.7mEq/L.3 This is based on a progressive increase in the frequency of magnesium deficiency seen with serum levels between 1.7mEq/L and 1.5mEq/L (from <10% to 90%), which is associated with an increased risk of morbidity, e.g., impaired glucose tolerance, type 2 diabetes mellitus, and mortality, e.g., sudden cardiac death.3,5 Magnesium is excreted by the kidneys, 6e24mEq/24h. Magnesium and calcium share the same transport system in the renal tubules and there is a reciprocal relationship between the amounts excreted. Address correspondence to: Andrew Wilcock, DM, FRCP, Hayward House Macmillan Specialist Palliative Care Unit, Nottingham University Hospitals NHS Trust, Nottingham NG5 1PB, United Kingdom. E-mail: andrew.wilcock@nottingham.ac.uk Accepted for publication: October 18, 2012.
2013 U.S. Cancer Pain Relief Committee. The scientific content of the article also appears on the website www.palliativedrugs.com, and is used with permission. 0885-3924/$ - see front matter