Ranolazine for Diabetic Peripheral Neuropathic Pain (DPNP)

Inclusion Criteria: 1. A minimum of 18 years of age; 2. Provided signed Informed Consent Form and Health Insurance Portability and Accountability Act (HIPAA) authorization for this study approved by the Institutional Review Board; 3. Patients must have diabetic peripheral neuropathic pain rated at an average level of six (6) or above as documented in daily diary prior to baseline visit and noted at Baseline Visit; 4. Diabetic on a stable insulin regimen or oral medication regimen as determined by the investigator \[It is recommended Hba1c \< 9.5%, making a note that lab normal values may vary among sites.\]; 5. Clinical Exam Results: 1. 5.07 Semmes-Weinstein Monofilament Test Subject does not sense monofilament or evokes an abnormal response in a minimum of two (2) out of five (5) test locations on the plantar surface of the foot. 2. Pin Prick Test Subject experiences allodynia, hyperalgesia, or sensory loss in two (2) out of five (5) test locations in the plantar surface - four (4) and dorsum - one (1) of the foot. 6. Willing and able to comply with the requirements of the protocol and follow directions from the clinic and research staff; 7. For female patients only: * Be post-menopausal (no menses for at least 2 years) or sterilized, * If subject of childbearing potential, not breastfeeding, has a negative pregnancy test at Baseline (pre-randomization, Day 0), has no intention of becoming pregnant during the course of the study, and is using one or more of the following contraceptive measures: 1. Stable regimen of hormonal contraception 2. Intra-uterine device 3. Condoms with spermicide 4. Diaphragm with spermicide Exclusion Criteria: 1. History of allergy or intolerance to ranolazine; 2. Any condition or concomitant medication that would preclude the safe use of ranolazine as outlined in the prescribing information sheet; 3. In the judgment of the investigator, any clinically-significant ongoing medical condition that might jeopardize the patient's safety or interfere with the absorption, distribution, metabolism or excretion of the study drug; 4. In the judgment of the investigator, clinically-significant abnormal physical findings during screening (excluding the patient's peripheral neuropathy condition); 5. Use participation in another experimental or investigational drug or device trial; 6. Pregnant or breast feeding; 7. Cirrhosis of the liver; 8. Psychological or addictive disorders (not limited to, but including for example, drug and/or alcohol dependency) that may preclude patient consent or compliance, or that may confound study interpretation; 9. Taking a moderate or strong CYP3A inhibitor (e.g. diltiazem, verapamil, ketoconazole, itraconazole, clarithromycin, erythromycin, nefazodone, nelfinavir, ritonavir, indinavir, and saquinavir); 10. Taking inducers of Cytochrome P450, family 3, subfamily A (CYP3A) (e.g. rifampin, rifabutin, rifapentine, phenobarbital, phenytoin, carbamazepine, and St. John's wort); 11. Renal impairment as defined by a calculated serum creatinine clearance of \< 30ml/min; 12. Lower back disorders where symptoms present similarly to DPNP; 13. Family history of long QT syndrome; 14. Congenital long QT syndrome; 15. Subjects taking tricyclic antidepressants; 16. Subjects taking anti-psychotic drugs; 17. Patient is taking \> 850mg metformin BID; 18. Any subjects currently taking pregabalin; 19. Any subjects currently taking gabapentin; 20. Any subject currently taking Metanx®; 21. Any subjects currently taking continuous long-term narcotics; 22. Grapefruit and grapefruit containing products; 23. Use of P-gp inhibitors - cyclosporine.