Hi, Zen Retard (diltiazem) and Lioresal (baclofen) are medications used to treat different conditions, but both can cause side effects. Zen Retard is a calcium channel blocker used to treat hypertension, angina pectoris, and arrhythmia. The common side effects of diltiazem include headache, dizziness, flushing, nausea, constipation, and fatigue. Joint pain and muscle pain are less common side effects of diltiazem, but they can occur in some people. Lioresal is a muscle relaxant used to treat spasticity caused by conditions such as multiple sclerosis, cerebral palsy, and spinal cord injury. The common side effects of baclofen are sleepiness, giddiness, weakness, vomiting sensation, and constipation. Muscle pain can also occur as a side effect of baclofen. Severe thigh pain could be a sign of a muscle or nerve problem and should be evaluated by a doctor. The pain may be related to your surgery or the medications you are taking. You should discuss your symptoms with your doctor and ask if any changes to your medications are necessary. They may recommend alternative treatments or adjust the dose of your current medications. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Priyanka, General & Family Physician