This pink, oval pill imprinted with M 5859 is a metaxalone 800 MG Oral Tablet, per the NIH.
Metaxalone is a human prescription drug. The active pharmaceutical ingredient is metaxalone and is classified as, "Centrally-mediated Muscle Relaxation [PE], Muscle Relaxant [EPC]."
This pill is made by a total of 13 firms: (1) CorePharma, LLC, (2) Lake Erie Medical & Surgical Supply DBA Quality Care Products LLC, (3) H.J. Harkins Company, Inc., (4) Dispensing Solutions, Inc., (5) REMEDYREPACK INC. , (6) Rebel Distributors Corp, (7) Unit Dose Services, (8) PD-Rx Pharmaceuticals, Inc., (9) Blenheim Pharmacal, Inc., (10) Preferred Pharmaceuticals, Inc, (11) St. Marys Medical Park Pharmacy, (12) STAT Rx USA LLC, and (13) Bryant Ranch Prepack.
There are 2 other pink pills that with a similar imprint: "M 5859". They may be a different dosage of the same drug or a different drug entirely.