MICRO-K
Clinical safety rating: caution
Comprehensive clinical and safety monograph for MICRO-K (MICRO-K).
Potassium is the principal intracellular cation, essential for maintaining cellular tonicity, electrical neutrality, and enzymatic reactions. It modulates neuromuscular transmission, cardiac contractility, and acid-base balance.
| Metabolism | Potassium ions are not metabolized; they are primarily excreted unchanged by the kidneys (90%), with minor losses via feces and sweat. |
| Excretion | Renal: approximately 90% of absorbed potassium is excreted in urine; biliary/fecal: less than 10% eliminated via feces. |
| Half-life | Not applicable; potassium is an electrolyte with no true elimination half-life; whole-body turnover half-life is approximately 12-24 hours, clinically relevant for dosing intervals. |
| Protein binding | None; potassium is not significantly bound to plasma proteins. |
| Volume of Distribution | 0.5-0.7 L/kg; total body water distribution; clinically indicates extensive intracellular uptake (98% intracellular). |
| Bioavailability | Oral: approximately 80-90% for Micro-K (extended-release); absorption occurs in small intestine. |
| Onset of Action | Oral: 30-60 minutes for increase in serum potassium; immediate-release formulations faster than extended-release. |
| Duration of Action | Oral: Extended-release (Micro-K) provides sustained release over 8-12 hours, with clinical effect lasting throughout dosing interval. |
Oral: 20-40 mEq (1-2 capsules) two to four times daily; maximum 100 mEq/day. Each capsule contains 8 mEq (600 mg) of potassium chloride in a wax matrix extended-release formulation.
| Dosage form | CAPSULE, EXTENDED RELEASE |
| Renal impairment | eGFR ≥60 mL/min: No adjustment. eGFR 30-59: Reduce dose by 25-50% and monitor potassium. eGFR 15-29: Reduce dose by 50-75% and monitor potassium. eGFR <15: Avoid use or use with extreme caution; maximum 20 mEq/day with frequent monitoring. |
| Liver impairment | No specific dosing adjustments recommended for hepatic impairment. Monitor potassium levels as hepatic disease may affect potassium homeostasis. |
| Pediatric use | Oral: <1 year: 1-2 mEq/kg/day divided 2-4 times. 1-18 years: 1-3 mEq/kg/day divided 2-4 times; maximum 100 mEq/day. Extended-release capsules not recommended for children unable to swallow whole capsules. |
| Geriatric use | Start at low end of dosing range (20-40 mEq/day) due to decreased renal function; maximum 100 mEq/day. Monitor renal function and potassium levels closely. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for MICRO-K (MICRO-K).
| Breastfeeding | Potassium is a normal constituent of breast milk. Supplemental potassium does not affect milk potassium content. M/P ratio not applicable. Use with caution if maternal renal function impaired. |
| Teratogenic Risk | Potassium chloride (Micro-K) is not associated with major congenital malformations. Normal maternal serum potassium levels are required for fetal development. Hypokalemia or hyperkalemia may increase risks. No trimester-specific risks documented. |
| Fetal Monitoring |
■ FDA Black Box Warning
None
| Serious Effects |
["Hyperkalemia (serum potassium >5.5 mEq/L)","Renal failure or severe renal impairment (e.g., oliguria, anuria)","Addison's disease","Acute dehydration","Concomitant use with potassium-sparing diuretics (e.g., amiloride, spironolactone, triamterene)","Concomitant use with eplerenone","Solid dosage forms in patients with delayed gastric emptying or esophageal compression"]
| Precautions | ["Hyperkalemia risk, especially in patients with renal impairment, diabetes, or those receiving potassium-sparing diuretics, ACE inhibitors, or ARBs","Suspect gastrointestinal obstruction or perforation with slow-release formulations; caution in patients with severe GI disorders","Use with caution in patients with cardiac disease, particularly those on digoxin","Monitor serum potassium levels regularly"] |
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| Monitor maternal serum potassium levels regularly, renal function, ECG in high-risk patients. Fetal monitoring not required unless maternal electrolyte disturbance occurs. |
| Fertility Effects | No known effects on fertility. Electrolyte balance maintenance may support normal reproductive function. |