Sodium bicarbonate
Sodium bicarbonate
Generic Name
Sodium bicarbonate
Mechanism
- Bicarbonate ion (HCO₃⁻) acts as a buffer:
- Reacts with excess hydrogen ions (H⁺) according to the equilibrium:
H⁺ + HCO₃⁻ ⇌ H₂CO₃ ⇌ CO₂ + H₂O
• This reaction consumes H⁺, raising the plasma pH and thereby correcting metabolic acidosis.
• In acid ingestion, it neutralizes free gastric acid, forming sodium chloride, water, and carbon dioxide, which is expelled by respiration.
• In dialysis settings, it buffers dialysate to maintain pH within 7.2–7.4, preventing diffusion of bicarbonate into the blood and reducing acid–base disturbances.
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Pharmacokinetics
| Parameter | Key Points |
| Absorption | Rapidly absorbed in the GI tract; 100 % bioavailability when taken orally. |
| Distribution | Distributes primarily in the extracellular fluid; volume of distribution ≈ 0.45 L/kg. |
| Metabolism | No significant metabolic conversion. |
| Elimination | Renal excretion via glomerular filtration and tubular secretion; half‑life ~5 h (shorter in renal disease). |
| Drug–Drug Interaction | May alter pH of plasma, affecting the ionization and clearance of other drugs (e.g., vancomycin, phenytoin). |
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Indications
- Acute or chronic metabolic acidosis (e.g., diabetic ketoacidosis, lactic acidosis, renal tubular acidosis).
- Acute ingestion of acidic toxins (hydrofluoric acid, sulfuric acid).
- Electrolyte correction (e.g., hypocalcemia secondary to acidosis).
- Buffering of drug infusions (e.g., cytotoxic agents, antibiotics).
- Dialysis – maintain dialysate pH; treat hyperkalemia in some protocols.
- Emergency cardiac conditions – to mitigate hyperkalemia by shifting K⁺ intracellularly (short‑term, adjunctive).
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Contraindications
- Severe respiratory failure / hypercapnia (CO₂ retention → paradoxical acidosis).
- Advanced renal failure or acute kidney injury (impaired bicarbonate excretion).
- Congestive heart failure/edema (risk of fluid overload).
- Hypernatremia, hyponatremia, or severe electrolyte imbalance.
- Pregnancy: Not teratogenic but use only if benefits outweigh risks.
Warnings:
• Monitor serum sodium, potassium, chloride, CO₂, and acid‑base status.
• Avoid rapid infusion rates to prevent hypernatremia, volume overload, and metabolic alkalosis.
• Use concomitant potassium supplementation when treating metabolic acidosis to prevent hypokalemia.
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Dosing
| Scenario | Typical Dose | Route | Notes |
| Metabolic acidosis (non‑renal) | 1–3 g (500–1500 mg) orally or IV per 100 mEq of deficit | Oral (pill/tablet) or IV (5 % NaHCO₃ 50 mEq/mL) | Dose individualized by serum bicarbonate < 22 mEq/L and anion gap. |
| Metabolic acidosis (renal) | 1–3 g orally or 50–100 mEq (1–2 mEq/kg) IV | Oral or IV | Adjust for renal impairment; monitor serum bicarbonate. |
| Acid ingestion | 1 mL/kg of 500 mEq/L solution | IV, but can give orally (if stable) | First dose 500‑1000 mEq; repeat as needed; avoid hypotonic solutions. |
| Dialysis buffering | 3 M or 5 M (1–3 mL) in dialysate | IV (in dialysis circuit) | Adjust pH to 7.2–7.4. |
| Hyperkalemia | 2–3 mEq/kg IV (maximum 200 mEq) | IV | Rapid infusion 4–5 mL/kg over 5–10 min; use with glucose–insulin. |
Administration Tips:
• For IV use, add to 5–10 % dextrose (5 % D) to cushion osmolarity and avoid rapid osmotic shifts.
• Do not crush tablets; prefer liquid form for IV or urgent oral use.
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Adverse Effects
| Adverse Effect | Commonality | Severity | Management |
| Nausea, vomiting, epigastric pain | Common | Mild | Slow or divide dose; consider antacids. |
| Hyponatremia / hypernatremia | Possible | Moderate to severe | Fluid restriction/adjust dose; monitor electrolytes. |
| Metabolic alkalosis | Common | Moderate | Reassess dose, correct underlying cause, supplement electrolytes. |
| Hypokalemia | Common | Moderate | Supplement potassium orally or IV. |
| Fluid overload & edema | Possible | Moderate | Use in cardiac patients cautiously; monitor weight/creatinine. |
| Hyperventilation / paradoxical acidosis (if CO₂ retention) | Rare | Severe | Stop therapy, provide ventilatory support. |
| Severe hypersensitivity (rare) | Rare | Severe | Discontinue; evaluate for underlying drug allergy. |
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Monitoring
- Arterial blood gases (ABG): pH, PaCO₂, PaO₂, bicarbonate level.
- Serum electrolytes: Na⁺, K⁺, Cl⁻, HCO₃⁻, Ca²⁺.
- Serum creatinine & BUN: renal function.
- Urine output: renal perfusion.
- Vital signs: BP, pulse, RR, SpO₂.
- Fluid balance: input/output charts, daily weights.
Frequency:
• Acute settings: every 30–60 min until stabilization.
• Chronic/metabolic: daily or as clinically indicated.
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Clinical Pearls
1. Avoid in chronic respiratory acidosis – the bicarbonate load can worsen CO₂ retention; instead focus on improving ventilation.
2. Use 1.5 % solution when treating severe acidosis in dialysis – it mitigates rapid osmolar shifts and is easier to titrate to the target pH.
3. Potassium must accompany bicarbonate in metabolic acidosis – even if serum K⁺ is normal, bicarbonate will drive K⁺ into cells, precipitating dangerous hypokalemia.
4. Administer with caution in heart failure – the sodium load can precipitate pulmonary edema; consider a low‑sodium formulation or split dosing.
5. In toxic ingestions, give 500–1 g orally or IV initially, then reassess – rapid neutralization is key but avoid overshooting, as this can induce alkalosis.
6. Remember its dual role – not just an antacid but also an electrolyte buffer; monitor both acid–base and electrolyte panels.
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• *This drug card is for educational purposes and should be used in conjunction with institutional guidelines and the prescribing information provided by regulatory agencies.*