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Kidney disease & electrolytes

Study essentials · Version 3 · Reviewed

Focused adult pharmacy study guide covering kidney-function assessment, medication safety, electrolyte emergencies and practical calculations. It does not replace a patient-specific prescription or monitored emergency protocol. Pediatric care, pregnancy, transplantation, complete dialysis prescriptions and comprehensive CKD anemia management require additional guidance.

Put it into practice

1. Assess kidney function in context

  • CKD requires a kidney abnormality lasting at least 3 months. Use cause, GFR and albuminuria together; G1 or G2 alone does not establish CKD without another marker of damage.
  • UACR categories: A1 below 30 mg/g; A2 30–300 mg/g; A3 above 300 mg/g. Confirm an unexpected abnormal result and establish chronicity.
  • GFR categories in mL/min/1.73 m²: G1 at least 90; G2 60–89; G3a 45–59; G3b 30–44; G4 15–29; G5 below 15.
  • AKI can be diagnosed by SCr rising at least 0.3 mg/dL within 48 hours, at least 1.5 times baseline within 7 days, or urine output below 0.5 mL/kg/hour for 6 hours. Normal urine volume does not rule out a qualifying creatinine change.
  • During AKI, review the medication list promptly and revisit doses as the trajectory changes. A single automated estimate cannot fully describe rapidly changing clearance.

Pause & recall
Can persistent albuminuria establish CKD when eGFR is above 60?

Sources: KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of CKD · KDIGO 2012 Acute Kidney Injury guideline

2. Match the estimate to the dose decision

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Match the estimate to the dose decision
TaskMethodSafety check
Deindex eGFRIndexed eGFR × BSA ÷ 1.73 = mL/minThis is not Cockcroft–Gault CrCl.
Cockcroft–Gault calculationMen: [(140 − age) × selected weight in kg] ÷ [72 × SCr in mg/dL]; historical equation multiplies this result by 0.85 for womenState the appropriate weight method; avoid arbitrary rounding of SCr. Use only when appropriate for the drug and patient.
Creatinine may be unreliableConsider combined creatinine–cystatin C estimate or measured GFR when greater precision is neededMarked muscle wasting and narrow therapeutic windows deserve particular attention.
Immediate-release gabapentin exampleThe label’s CrCl >15–29 mL/min row is 200–700 mg/day, once dailyThis is a renal-table example, not a universal starting dose; assess indication, sedation and titration.
Hemodialysis medication reviewVerify the dialysis modality, drug removal, scheduled dose and any post-HD supplementDo not assume every drug needs the same timing or an extra dose.

Pause & recall
Why are indexed eGFR, nonindexed eGFR and Cockcroft–Gault CrCl different?

Sources: FDA renal impairment pharmacokinetic study guidance · KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of CKD · NEURONTIN U.S. prescribing information

3. Preserve kidney function and manage medicines

  • For albuminuric CKD, use a tolerated ACEi or ARB when indicated. Avoid routine combinations of ACEi, ARB and direct renin inhibitors. Check BP, SCr and potassium after starting or increasing therapy; a rise in SCr above 30% within 4 weeks prompts assessment.
  • An SGLT2 inhibitor is recommended for adults with CKD and eGFR at least 20 plus UACR at least 200 mg/g, or heart failure regardless of albuminuria. Review the selected product’s indication and precautions. A small initial eGFR dip may be expected.
  • For CKD associated with type 2 diabetes, finerenone eligibility includes potassium and renal function checks. Do not initiate if potassium is above 5.0 mEq/L; initiation is not recommended at eGFR below 25. Check potassium about 4 weeks after starting or changing the dose and periodically afterward. Its heart-failure dosing algorithm differs.
  • During vomiting, dehydration or serious acute illness, review NSAIDs and renally cleared medicines promptly. Any temporary prescription hold needs an individualized indication, monitoring plan and explicit restart instructions.
  • Choose dialysis timing with nephrology using symptoms, laboratory complications, fluid status, nutrition and the person’s goals. Preparation often begins before a reason to initiate dialysis arises.

Pause & recall
Which potassium threshold prevents starting finerenone, and when should follow-up be arranged?

Sources: KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of CKD · KERENDIA U.S. prescribing information

4. Potassium: protect, shift, remove and reassess

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Potassium: protect, shift, remove and reassess
ProblemImmediate learning pointFollow-up
Hyperkalemia with toxic ECG changesIV calcium stabilizes the heart; it does not remove potassiumUse monitored emergency treatment and repeat assessment.
Temporarily shifting potassiumInsulin with glucose moves potassium into cells; beta₂ agonists may be an adjunctCheck glucose repeatedly after insulin; UKKA guidance monitors through 6 hours. Recheck potassium for rebound.
Removing potassiumAddress the cause; use a suitable removal strategy, including urgent KRT for refractory life-threatening abnormalitiesU.S. patiromer and LOKELMA labels do not position these as emergency rescue for life-threatening hyperkalemia.
Potassium replacementConcentrated KCl must be diluted and given as a controlled IV infusion, never direct IV pushVerify kidney function, total potassium from all products, rate and monitoring.
Persistent hypokalemia with low magnesiumCorrect magnesium as part of an individualized potassium replacement planRenal impairment increases magnesium accumulation risk.

Pause & recall
Why can a potassium value improve after insulin and then rise again?

Sources: UK Kidney Association acute hyperkalemia guideline · Potassium chloride for injection concentrate, Hospira U.S. labeling · Magnesium sulfate injection 50%, Henry Schein repackaged U.S. labeling · VELTASSA U.S. prescribing information · LOKELMA U.S. prescribing information · Hypokalemia: a clinical update

5. Do not interchange binder counseling

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Do not interchange binder counseling
MedicineAdministration pointMonitor or clarify
PatiromerSeparate other oral medicines by at least 3 hours unless the label documents no important interactionPotassium, magnesium, bowel symptoms; levothyroxine requires separation.
Sodium zirconium cyclosilicateGenerally separate oral medicines by at least 2 hours; exceptions depend on pH-dependent solubilityPotassium and edema; each 5 g contains about 400 mg sodium, with uncertain absorption.
Sevelamer carbonateTake prescribed doses with meals to bind dietary phosphatePhosphate response, GI tolerance and drug interactions.
CKD–mineral/bone assessmentInterpret serial phosphate, calcium and PTH togetherAvoid hypercalcemia and unnecessary calcium loading; binder choice is individualized.

Pause & recall
Which binder needs meals, which needs magnesium follow-up, and which adds sodium?

Sources: VELTASSA U.S. prescribing information · LOKELMA U.S. prescribing information · RENVELA U.S. prescribing information · KDIGO 2017 CKD–mineral and bone disorder guideline update synopsis

6. Recognize the urgent electrolyte presentation

  • Seizure or other severe symptoms from hypotonic hyponatremia require urgent monitored hypertonic saline treatment. Use an experienced team and an established protocol; oral fluid restriction alone is inadequate rescue.
  • After the initial controlled rise relieves symptoms, limit further correction and monitor sodium and urine output closely. Chronic or uncertain-duration hyponatremia is vulnerable to ODS when correction is excessive, especially with malnutrition or alcohol use disorder. Escalate an unexpectedly rapid rise promptly.
  • Marked tetany, seizures or cardiac abnormalities with hypocalcemia warrant urgent monitored IV calcium and evaluation of the cause. Check magnesium; postoperative parathyroid dysfunction is one possible cause.
  • Absent reflexes and respiratory depression during IV magnesium treatment are toxicity warning signs. Stop the infusion, obtain emergency clinical support and prepare specific treatment as directed. Severe renal impairment increases risk.

Pause & recall
Why is immediate normalization of sodium not the goal during a hyponatremic seizure?

Sources: Society for Endocrinology: emergency management of symptomatic hyponatraemia in adults · Second International Workshop: Evaluation and Management of Hypoparathyroidism · Magnesium sulfate injection 50%, Henry Schein repackaged U.S. labeling

7. Interpret acid–base data in a sequence

  • Identify acidemia or alkalemia, then determine whether the bicarbonate or PaCO₂ change explains the pH direction. A near-normal pH can still conceal mixed disorders.
  • Anion gap excluding potassium = Na⁺ − (Cl⁻ + HCO₃⁻), using consistent mEq/L units. Interpret the result with the laboratory reference and albumin; low albumin can hide an elevated gap.
  • For metabolic acidosis, Winter’s expected PaCO₂ = 1.5 × HCO₃⁻ + 8 ± 2 mm Hg. Measured PaCO₂ above the range suggests an additional respiratory acidosis; below the range suggests respiratory alkalosis.
  • Vomiting can cause metabolic alkalosis through gastric acid and chloride loss. Evaluate the cause and volume/electrolyte status instead of treating an isolated bicarbonate number.
  • In CKD with clinically important metabolic acidosis, consider dietary and/or pharmacologic treatment under an individualized plan. KDIGO gives bicarbonate below 18 mmol/L as an example and advises monitoring bicarbonate, BP, potassium and fluid status.

Pause & recall
In metabolic acidosis, what does a measured PaCO₂ above Winter’s expected range suggest?

Sources: Acid–Base Disorders in the Critically Ill Patient, CJASN · KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of CKD

8. Calculate, then perform the clinical safety check

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Calculate, then perform the clinical safety check
CalculationWorked resultBefore administration
Nonindexed eGFR36 × 2.20 ÷ 1.73 = 45.78 → 46 mL/minApply the metric supported by the drug’s dosing evidence.
Potassium phosphates content18 mmol ÷ 3 mmol/mL = 6 mL; 6 × 4.4 = 26.4 mEq potassiumInclude the potassium load; check dilution, compatibility, rate and relevant labs.
Sodium bicarbonate stock volume75 mEq ÷ 1 mEq/mL = 75 mL of the specified 8.4% productThis is stock volume only, not final admixture volume or a treatment recommendation.
UnitsmEq describes charge; mmol describes amount of substanceFor monovalent sodium/potassium, 1 mmol = 1 mEq. Do not apply that relationship to divalent ions.

Pause & recall
A dose supplies 18 mmol phosphorus from a 3 mmol/mL vial containing potassium 4.4 mEq/mL. How much potassium accompanies it?

Sources: FDA renal impairment pharmacokinetic study guidance · NEURONTIN U.S. prescribing information · Potassium phosphates injection, American Regent U.S. prescribing information · Sodium bicarbonate injection 8.4%, Exela U.S. labeling

Abbreviations

CKD
chronic kidney disease
AKI
acute kidney injury
eGFR
estimated glomerular filtration rate
CrCl
creatinine clearance
UACR
urine albumin-to-creatinine ratio
BSA
body surface area
SCr
serum creatinine
ACEi
angiotensin-converting enzyme inhibitor
ARB
angiotensin II receptor blocker
SGLT2
sodium–glucose cotransporter 2
NSAID
nonsteroidal anti-inflammatory drug
KRT
kidney replacement therapy
HD
hemodialysis
ECG
electrocardiogram
IV
intravenous
PTH
parathyroid hormone
ODS
osmotic demyelination syndrome
AG
anion gap
PaCO₂
arterial partial pressure of carbon dioxide
HCO₃⁻
bicarbonate
mEq
milliequivalent
mmol
millimole

Sources & verification

Guide reviewed . Source checks are dated below. These selected teaching points use the guidance and product references below. Confirm current labeling, the patient's circumstances, and local protocols before applying a regimen.

  1. KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of CKD — Recommendations 3.6.1–3.7.3; practice points 4.2.1–4.3.3 and 5.4.1–5.4.3; Tables 1–3 · Checked https://kdigo.org/wp-content/uploads/2024/03/KDIGO-2024-CKD-Guideline.pdf
  2. KDIGO 2012 Acute Kidney Injury guideline — 2.1.1 and Table 2: definition and staging; 5.1.1–5.1.2: urgent kidney replacement · Checked https://kdigo.org/wp-content/uploads/2016/10/KDIGO-2012-AKI-Guideline-English.pdf
  3. FDA renal impairment pharmacokinetic study guidance — IV.A: renal function estimates and nonindexed GFR; sponsor guidance, not a replacement for current drug-specific dosing instructions · Checked https://www.fda.gov/media/78573/download
  4. NEURONTIN U.S. prescribing information — 2.3 Table 1: renal function dose regimens; 2.5: dose reduction/discontinuation; 5.2: sedation · Checked https://labeling.pfizer.com/ShowLabeling.aspx?id=630
  5. KERENDIA U.S. prescribing information — 2.1–2.3, 4 and 5.1: initiation, CKD associated with type 2 diabetes dosing and hyperkalemia · Checked https://dailymed.nlm.nih.gov/dailymed/fda/fdaDrugXsl.cfm?setid=fc726765-5d5a-4d6e-b037-b847bda9fb7c
  6. UK Kidney Association acute hyperkalemia guideline — Hospital guidance 14–18: ECG, calcium, intracellular shift, potassium removal, glucose and potassium monitoring · Checked https://guidelines.ukkidney.org/hyperkalaemia/
  7. Potassium chloride for injection concentrate, Hospira U.S. labeling — Warnings: potentially fatal cardiac adverse reactions with undiluted intravenous administration; Dosage and Administration · Checked https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=559a0a8c-a8fe-40a5-b196-21f9308780ab
  8. Magnesium sulfate injection 50%, Henry Schein repackaged U.S. labeling — Clinical Pharmacology; Warnings; Precautions; Overdosage: renal clearance, reflexes and respiratory depression · Checked https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=c255b8a9-68da-49c1-897b-bc18b731e459
  9. VELTASSA U.S. prescribing information — 1, 2.1, 5.2 and 7: emergency-use limitation, separation, magnesium and levothyroxine interaction · Checked https://dailymed.nlm.nih.gov/dailymed/fda/fdaDrugXsl.cfm?setid=bf002984-d6c9-46df-aecb-a07733f763c1
  10. LOKELMA U.S. prescribing information — 1, 2.3, 5.2 and 7: emergency-use limitation, administration, sodium/edema and interactions · Checked https://dailymed.nlm.nih.gov/dailymed/fda/fdaDrugXsl.cfm?setid=8833d6e6-33ab-4ea9-b78f-3ec30a904ef8&type=display
  11. Hypokalemia: a clinical update — Causes and treatment: coexisting magnesium deficiency and refractory potassium depletion · Checked https://pmc.ncbi.nlm.nih.gov/articles/PMC5881435/
  12. RENVELA U.S. prescribing information — 2.1: dosing with meals; 12.1: phosphate binding · Checked https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=e6328460-a57b-450b-a48c-6dcd4b476360
  13. KDIGO 2017 CKD–mineral and bone disorder guideline update synopsis — 4.1.1–4.1.8: serial calcium/phosphate/PTH, hypercalcemia and phosphate binder selection · Checked https://kdigo.org/wp-content/uploads/2017/02/KDIGO-2017-CKD-MBD-GL-Update-Synopsis.pdf
  14. Society for Endocrinology: emergency management of symptomatic hyponatraemia in adults — Treatment recommendations and management of over-correction, pages 3–5 · Checked https://www.endocrinology.org/media/xhrhxhxm/emergency-management-of-severe-and-moderately-severely-symptomatic-hyponatraemia-in-adult-patients-2022.pdf
  15. Second International Workshop: Evaluation and Management of Hypoparathyroidism — Emergency management of severe acute hypocalcemia, page 8 · Checked https://www.endocrinology.org/media/txbkbhvb/jbmr_4691.pdf
  16. Acid–Base Disorders in the Critically Ill Patient, CJASN — Approach to Acid-Base Disorders; Table 1; Metabolic Alkalosis and Nasogastric Suction or Vomiting · Checked https://pmc.ncbi.nlm.nih.gov/articles/PMC10101555/
  17. Potassium phosphates injection, American Regent U.S. prescribing information — 2.1–2.3, 3 and 5.1–5.4: dilution, phosphorus/potassium content, compatibility and monitoring · Checked https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=41a85cca-c463-4f39-9335-177b04c290a9
  18. Sodium bicarbonate injection 8.4%, Exela U.S. labeling — Contraindications; Warnings; How Supplied: 1 mEq sodium and bicarbonate per mL · Checked https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=2f05947f-a489-4298-a871-90db75b2a6c5

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