R 637 (Gabapentin 800 mg) Pill with imprint R 637 is Gray, Capsule-shape and has been identified as Gabapentin 800 mg. It is supplied by Actavis. Gabapentin is used in the treatment of postherpetic neuralgia; epilepsy and belongs to the drug class gamma-aminobutyric acid analogs. Risk cannot be ruled out during pregnancy. Gabapentin 800 mg… Continue reading Gabapentin 800mg, Gabapentin 600mg – Actavis Pharma, Inc.