Epitochem

Sodium Citrate

Sodium Citrate

Sodium citrate dihydrate appears as colorless, monoclinic crystals or a white crystalline powder with a cooling, saline taste. It is slightly deliquescent in moist air and efflorescent in warm, dry air. The dihydrate form is the standard in most pharmacopeias, though the USP allows both anhydrous and dihydrate forms.

Chemical Name and CAS Registry Number: Trisodium 2-hydroxypropane-1,2,3-tricarboxylate dihydrate[6132-04-3]

Functional Category: Alkalizing agent; buffering agent; emulsifier; sequestering agent.

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Pharmacopeial Specifications

Test JP 2001 PhEur 2005 USP 28
Identification ✓✓ ✓ ✓
pH (5% w/v solution) 7.5–8.5 — —
Appearance of solution ✓ ✓ —
Acidity/Alkalinity ✓✓ ✓ —
Water Content 10.0–13.0% 11.0–13.0% 10.0–13.0%
Sulfate ≤ 0.048% ≤ 150 ppm —
Heavy Metals ≤ 10 ppm ≤ 10 ppm ≤ 0.001%
Assay (anhydrous basis) ≥ 99.0% 99.0–101.0% 99.0–100.5%

Applications in Pharmaceutical Formulation

Sodium citrate dihydrate is used as:

  • A buffering agent (0.3–2.0%) in pharmaceutical formulations.
  • A sequestering agent (0.3–2.0%) to bind metal ions.
  • A pH adjuster in ophthalmic solutions (0.1–2.0%) and injections (0.02–4.0%).
  • A blood anticoagulant, alone or in combination with other citrates.
  • A therapeutic agent for treating cystitis and metabolic acidosis due to diarrhea.

Comments

Sodium citrate is a well-tolerated excipient with broad pharmaceutical and food applications. It is included in the FDA Inactive Ingredients Guide and approved for use in parenteral and nonparenteral formulations worldwide. Citrates, however, can enhance aluminum absorption, which is a concern for patients with renal impairment.

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