MICRO-K
Clinical safety rating
cautionComprehensive 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. |
| Molecular Weight | 74.55 |
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 | Potassium chloride is generally considered safe when used at therapeutic doses; however, use only if clearly needed. No known teratogenicity. |
| 2nd trimester | Safe at therapeutic doses. Monitor serum potassium and renal function. No known fetal risk. |
| 3rd trimester | Use with caution near term due to potential for hyperkalemia in the mother; may affect fetal cardiac function if severe. Monitor closely. |
Clinical note
Comprehensive clinical and safety monograph for MICRO-K (MICRO-K).
| Placental transfer | Potassium freely crosses the placenta; maternal-fetal gradient maintained within narrow limits. |
| Breastfeeding | Potassium is a normal constituent of breast milk. Supplementation does not significantly alter milk potassium concentration. Use with caution in nursing mothers, especially if renal impairment or high doses. |
| Lactation Rating | L1 (Safe) |
| 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 | 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. |
■ FDA Black Box Warning
None
| Serious Effects |
HyperkalemiaSevere renal impairment with oliguria or azotemiaAddison's diseaseConcurrent use of potassium-sparing diureticsSolid oral dosage forms in patients with gastrointestinal motility disorders or strictures
| 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 |
| Food/Dietary | Avoid high-potassium foods (e.g., bananas, oranges, spinach, potatoes, tomatoes) and potassium-based salt substitutes. Consuming large amounts of these may increase risk of hyperkalemia. |
| Clinical Pearls | Micro-K (potassium chloride extended-release) is used to prevent and treat hypokalemia. Avoid use in severe renal impairment, metabolic acidosis, or conditions with high potassium levels. Slow-release formulations reduce GI irritation but may be contraindicated in patients with GI motility disorders. Do not crush or chew capsules; administer with food and a full glass of water. Monitor serum potassium and renal function regularly. |
| Patient Advice | Take this medication with food and a full glass of water to reduce stomach upset. · Swallow the capsule whole; do not crush, chew, or open it. · Do not suddenly stop taking this medication without consulting your doctor. · Avoid salt substitutes or potassium-containing supplements unless approved by your doctor. · Seek immediate medical attention if you experience signs of high potassium levels: muscle weakness, irregular heartbeat, or tingling in hands/feet. |
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