Hypokalemia & Hyperkalemia - Clinical Pharmacology PDF

█ Hypo okalemia a  Potassium is the major intracellula ar cation. 98% of K+ in the bo dy is found in the intra acellular co ompartment, leaving g 2% in exttracellular fluid spacees.  Ren + nal K excrretion occu urs from thhe DCT...

█ Hypo okalemia a  Potassium is the major intracellula ar cation. 98% of K+ in the bo dy is found in the intra acellular co ompartment, leaving g 2% in exttracellular fluid spacees.  Ren + nal K excrretion occu urs from thhe DCT and d is mediated by ald a Na+ dosterone and delivery to thee distal nep phron.  Hyppokalemia is defined as serum K+ 5 mEq/L. m It can c result ffrom trans scellular + + shifft of K , or decreased d renal exc cretion of K (as in chhronic renaal failure).  Thee most co ommon manifestati m ions are muscle paralysis, p palpitations, high peaaked T wavve and sho ort QT interrval in the ECG.  Beccause K is + i usually exchange ed with H+ at the DCT,D hypeerkalemia is i often linkeed to meta abolic acid dosis. Druugs cause transcellu of K+ (from ular shift o m tissue to o plasma):: Insu ency and β-blockers: they ↓ transmembra ulin deficie ane Na+/K++-ATPase activity. a ugs that ↓ renal excrretion of K +: Dru K+ sparing diu uretics, AC CEIs, NSAIIDs, cyclos sporins. 101  Management  Mild hyperkalemia: could be corrected by diuretics and oral cation exchange resins (Polystyrene sulfonate) to promote the exchange of Na+ for K+ in the GIT.  Severe hyperkalemia with ECG changes:  Intravenous calcium gluconate to reduce cardiac toxicity (↓ membrane excitability). The usual dose is 10 mL of a 10% solution infused over 2 to 3 minutes.  Intravenous insulin with glucose: 20 U regular insulin mixed with 500 ml D5W.  Correct metabolic acidosis with i.v. NaHCO3 solution.  Hemodialysis is reserved for patients with renal failure or with life-threatening hyperkalemia resistant to other treatment. Part 6: Pharmacological manipulation of the urine pH Normal urine pH is 5.2-6.5. It is possible, by the use of pharmacological agents, to produce urinary pH values ranging from ~ 5 to 8.5. █ Alkalinization of the urine  Indications:  To enhance excretion of acidic drugs and organic compounds e.g. aspirin, sulfonamides, and uric acid.  To enhance dissolution of uric acid and cystine stones.  To relieve dysuria (burning micturition) in some cases of bladder infection.  Alkalinizing agents:  Oral: sodium and potassium citrate salts: citrate is metabolized into bicarbonate which is excreted in urine.  Intravenous bicarbonate solution: contains 5% NaHCO3. █ Acidification of the urine  Indications:  It is rarely used clinically except in a specialized test to discriminate between different kinds of renal tubular acidosis.  It can be very dangerous in cases of renal or hepatic impairment.  Acidifying agents:  Oral: ascorbic acid > 2 g/d.  Intravenous ammonium chloride (NH4Cl) solution. 102