Tuesday, July 28, 2015

Phenytoin Compatibility

  • Phenytoin has a pH in the range of 10 - 12.3. It will only stay in solution when the pH is considerably alkaline (about 10 - 12). 
  • The mixing of phenytoin sodium injection with other drugs is not recommended
Compatible diluents
Incompatible diluent

  1. 0.9% sodium chloride
  2. Lactated Ringer's injections



  1. Dextrose containing solutions
  • as it provokes significant precipitation of phenytoin sodium injection via interruption of the cosolvent effect of propylene glycol.
  • crystals were observed in all dextrose solutions after dilution.
  • factors other than pH and cosolvent concentration may affect phenytoin stability in dextrose solutions.
Administration
  • increased risk of adverse cardiovascular reactions associated with rapid administration, IV should not exceed 50 mg per minute in adults. 
  • In pediatric patients, the drug should be administered at a rate not exceeding 1-3 mg/kg/min or 50 mg per minute, whichever is slower
  • As non-emergency therapy, Phenytoin Sodium Injection should be administered more slowly as either a loading dose or by intermittent infusion. 
  • Because of the risks of cardiac and local toxicity associated with IV phenytoin, oral phenytoin should be used whenever possible
  • Because of the risk of local toxicity, IV Phenytoin Sodium Injection should be administered directly into a large peripheral or central vein through a large-gauge catheter. 
  • Patency of the IV catheter should be tested with a flush of sterile saline. 
  • Each injection of parenteral Phenytoin Sodium Injection should then be followed by a flush of sterile saline through the same catheter to avoid local venous irritation due to the alkalinity of the solution
Storage:
  • Store at 20°-25°C, excursions permitted to 15°-30°C
  • The diluted infusion mixture (Phenytoin Sodium Injection plus normal saline) should not be refrigerated. 
  • If the undiluted parenteral Phenytoin Sodium Injection is refrigerated or frozen, a precipitate might form: this will dissolve again after the solution is allowed to stand at room temperature. 
  • The product is still suitable for use. A faint yellow coloration may develop, however this has no effect on the potency of the solution.
References:
  1. http://www.drugs.com/pro/phenytoin-sodium.html
  2. https://www.medicines.org.uk/emc/medicine/27054
  3. http://www.ncbi.nlm.nih.gov/pubmed/22223379

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