Cause:Renal failure, often parallels K⁺ incr. Chronic Mg-containing antacid and laxative use. Enemas, esp in megacolon, with Mg-containing soaps

Pathophys:Avg qd intake = 20-40 mEq; total body stores = 2000 mEq, half in bones, rest intracellular

Less common than hypomagnesemia

Sx:Difficult defecation, urination; nausea; drowsiness at pharmacologic doses only

Si:Depressed DTRs, hypotension

Heart block, respiratory paralysis

Lab:

Chem:Mg⁺⁺ >2.2 mEq/L

Noninv:EKG shows heart block