Formulation in Pharmacy Practice  - eMixt

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Pyrimethamine is practically insoluble in water, and slightly soluble in alcohol.

The stability of pyrimethamine in a base of methylcelulose and syrup has been investigated (1). Although not formally studied, short-term stability in commercial suspending bases would be expected.


Formula (1)

Pyrimethamine Suspension 2mg/mL

Pyrimethamine Tablets 25mg 40 
Methylcellulose Solution 1% 250  mL
Syrup BP 250  mL
Grind tablets to a powder.  Add a little methylcellulose and syrup to form a paste.  Add to volume.
Expiry:  30 days.
Stability:  Chemically stable for 91 days.
Storage:  Protect from light in airtight containers.  Refrigerate.
Shake the bottle

  1. Nahata M.C., Morosco R.S., Hipple H.T.  Stability of pyrimethamine in a liquid dosage formulation stored for three months.  
    Am J Health-Syst Pharm
    1997; 54: 2714-2716.[PubMed Link]
  2. Pyrimethamine Stabilis database

Formulation in Pharmacy Practice
Page updated April 2014