Recent research suggests the possibility that when phenylbutazone is co-administered with methocarbamol (Robaxin), the clearance time of the methocarbamol is delayed. Accordingly, if you are administering phenylbutazone in conjunction with methocarbamol, the recommended withdrawal time for the administration of methocarbamol should be extended. We strongly recommend that you consult with your veterinarian regarding the use of these medications in combination.
Please also be advised that the recommended dosage and withdrawal time recommendations contained in the new Uniform Medication and Drug Testing Program do not apply when using compounded medications. There is limited regulatory oversight and quality control on how these medications are prepared.