Pharmaceutical prepn. comprises: (a) a salt of ranitidine (I) with a bismuth complex of tartaric or citric acid; and (b) an alkali salt. Pref. the salt is e.g. -N-(Q)-N'-methyl-2-nitro -11-ethenediamine-2-hydroxy -123-propanetricarboxylate -bismuth (3+).

A potassium salt useful in the production of N-substituted-1-alkylthio-2-nitroethenamines is produced by the reaction of the dipotassium salt of nitrodithioacetic acid with certain straight chain alkylamines thereby converting only one of the KS-groups to an alkylamine group. The resulting monopotassium salt may be alkylated to produce the required N-substituted-1-alkylthio compound which may be reacted with a suitable amine to produce the histamine H2-antagonist ranitidine.

The bitter taste of ranitidine may be masked by forming an adsorbate with a synthetic cation exchange resin. The adsorbate is particularly suitable for use in pharmaceutical compositions for oral administration such as chewable or suckable tablets granules and aqueous or non-aqueous suspensions.