The invention also provides intermediates useful in the production of pregabalin.

A solid pharmaceutical composition containing pregabalin is described.

Preferred A2d ligands are gabapentin and pregabalin.

Following a dose of radiolabelled pregabalin, approximately 98 % of the radioactivity recovered in the urine was unchanged pregabalin.

A Pregabalin having a low level of 3-isobutylglutaric acid is provided.

Preferred treatments employ gabapentin or pregabalin.

Particularly preferred alpha-2-delta ligands are gabapentin and pregabalin.

Compounds of formula (I) are useful for preparing pregabalin.

The composition exhibits satisfactory drug efficacy despite the low pregabalin content (3 wt% or less) and the fact that pregabalin is the sole active ingredient.

Following a dose of radiolabelled pregabalin, approximately 98% of the radioactivity recovered in the urine was unchanged pregabalin.

The N-methylated derivative of pregabalin, the major metabolite of pregabalin found in urine, accounted for 0.9 % of the dose.

The invention also relates to process for preparing these intermediates and Pregabalin.

The N-methylated derivative of pregabalin, the major metabolite of pregabalin found in urine, accounted for 0.9% of the dose.

The invention relates to crystalline 'forms of Pregabalin and their process o preparation.

However, administration of pregabalin with food has no clinically significant effect on the extent of pregabalin absorption.