organism from the bowel or result in clinical improvement Aminoglycosides, which can cause neuromuscular blockade, should be avoided Periodic Paralysis Familial periodic paralysis is a rare illness, inherited in an autosomal-dominant fashion, which results in episodes of severe weakness associated with an abnormality of circulating potassium during attacks Two major forms of illness —hyperkalemic and hypokalemic—are recognized A third type, normokalemic, has been described but most likely represents a rare variant of the hyperkalemic variety Other disorders that can produce weakness and electrolyte abnormalities, such as use of corticosteroids or diuretics, thyrotoxicosis, hyperaldosteronism, and renal insufficiency, may mimic the periodic paralyses The serum potassium abnormalities in familial periodic paralysis are believed to be epiphenomena of yet undelineated muscle membrane abnormalities Characteristically, a previously well patient develops a flaccid weakness in his or her trunk and upper thighs, and the weakness gradually involves the remainder of the skeletal muscles Deep tendon reflexes are diminished The attacks last from hours to days, and between the attacks, muscular strength is usually normal, although a minority of patients have residual muscular weakness In both forms of periodic paralysis, ECG changes consistent with the serum potassium abnormality may be noted and cardiac arrhythmias may rarely arise Hypokalemic periodic paralysis, the most common type, occurs primarily in adolescents and young adults Trigger factors include vigorous exercise, heavy carbohydrate meals, alcohol, and the cold During an attack, potassium levels are usually to 2.5 mEq/L Emergency treatment of hypokalemic periodic paralysis includes oral, or rarely IV, potassium Prophylactically, patients should avoid precipitants such as vigorous exercise or large carbohydrate loads Recurrences may be prevented with spironolactone or acetazolamide The hyperkalemic form usually begins in the first decade of life, and attacks occur predominantly during the period of rest after vigorous exercise or after fasting Attacks are typically associated with myotonia The episodes are more common than in hypokalemic paralysis but often last less than a few hours During the attack, plasma potassium level can be moderately elevated, although it is often in the upper normal range Attacks of hyperkalemic periodic paralysis are often brief enough that acute treatment is unnecessary In severe attacks, inhaled albuterol and IV calcium gluconate may be helpful Acetazolamide, thiazide diuretics, and albuterol have been used for prevention of recurrences