Ibudilast in the Treatment of Medication Overuse Headache

Inclusion criteria: * Regular use, for at least 3 months, of opioid-containing analgesics on ≥ 10 days/month * Headache present on at least 15 days/month, for at least 2 months * Headache developed or markedly worsened during medication overuse * Primary indication for analgesics is headache disorder Exclusion criteria: * Unable to provide written informed consent * Age \< 18 years at time of screening * Unable to read and write in English * Receiving tramadol regularly * Taking triptans \> 4 days/month * Taking opioids for reasons other than headache (e.g. other pain conditions, cough, bowel motility) * Severe psychiatric disorders * Other chronic pain conditions likely to interfere with qualitative sensory testing (e.g. trigeminal neuralgia, arthritis) * Diabetic neuropathy * Recent or current active infection, determined to be clinically significant by the Principal investigator * Known active inflammatory diseases such as rheumatoid arthritis * History of cerebrovascular disorder * Recent history of significant trauma, as determined by the Principal Investigator including major surgery within the previous 2 months * Recent history of drug or alcohol abuse * Spinal cord injury * Any clinically significant findings on screening blood sample results * Current malignancy * Known hypersensitivity to ibudilast or excipients in Pinatos® formulation * Renal or hepatic impairment, defined as baseline GFR (as calculated by the Cockcroft-Gault equation) of \< 60 mL/min or LFTs \> 3 times the upper limit of normal * For females of childbearing potential: * Pregnancy * Lack of adequate contraception (abstinence, double barrier method, intrauterine device, surgical sterilization (self or partner), hormonal contraceptive methods (oral, injected, or implanted) * Breastfeeding