Hello, I read your message and understood your medical issue. Levodopa and Carbidopa are two drugs that are taken together to reduce the symptoms of the Parkinson s disease. There is no study till today that the combination of levodopa/carbidopa and midodrine causes excessive high blood pressure when are given together. The fact is that each of these drugs may cause high blood pressure independently. Levo/carbidopa may cause high blood pressure or low blood pressure but if given in the exact dosage these drugs are safe. Much more careful needs for the midodrine. This drug can evaluate the supine blood pressure too much and doctors prescribe it only in the cases when the lives of patients are significantly impaired despite the rigorous clinical care. The decision whether to take midodrine or not must be taken carefully. Your brother in law needs this drug has the orthostatic hypotension impairs his everyday life. The midodrine drug is first given that is observed what clinical improvements it can bring. If after the drug intake the quality of life is improved and if the systolic blood pressure measured after one minute after standing is increased than midodrine must be administered. My advice is that he must take the drug then you can take an effort to measure his blood pressure one minute after he is standing up. Remember the numbers you will found and discuss them with his doctor. Hope this is helpful for you. Dr.Albana