Formulation in Pharmacy Practice - eMixt

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Amitriptyline hydrochloride is freely soluble in water but has a bitter, burning taste and local anaesthetic properties.  Commercially available suspensions are usually formulated as amitriptyline embonate which is more palatable.
An oral liquid prepared from amitriptyline hydrochloride tablets would contain a solution of the drug and a suspension of insoluble excipients.  This preparation would be relatively unpalatable.
Amitriptyline hydrochloride is reported to be stable in aqueous solution for up to 8 weeks at room temperature if protected from light.1  Amitriptyline injection has pH of 4 - 6.  Metallic ions, which can leach from some types of glass, can accelerate the degradation of amitriptyline whereas the addition of 0.1% disodium edetate reduces oxidative degradation.2
An oral liquid prepared from crushed tablets of amitriptyline hyrochloride in water may be relatively stable if stored in amber plastic containers and protected from light.  However, the clinical use of such a product is probably limited by its poor taste.

  1. Buckles J, Walters V.  The stability of amitriptyline hydrochloride in aqueous solution.
    J Clin Pharm 1976; 1: 107-12.
  2. Enever RP, Li Wan Po A, Shotton E.  Factors influencing the decomposition rate of amitriptyline hydrochloride in aqueous solution.  J Pharm Sci 1977; 66: 1087-89

Formulation in Pharmacy Practice
Page Updated August 2011