I was told to have a breast biopsy, but the doctor said it could not be done with a local anesthetic, but she would have to use MAC. I have multiple chemical sensitivity, and am allergic to many medications, as well as plastics, all contrast dyes, ester anesthetics, etc.etc. etc. I had a very negative reaction to Versed (severe brochospasms for over a month) following a colonoscopy in 2001. I would like to know which drugs are used in MAC. The doctor said it couldn`t be done with a local, because it`s "easier on the doctor" if the patient is not awake. Apparently, the patient`s allergies/sensitivities are not as important, but I have not found any other doctors in my area willing to do it with a local anymore. Thank you. 

MAC is not a specific medication, or set of medications. In fact, MAC (Monitored Anesthesia Care) is a difficult term to define (see previous questions on this topic) and refers to some level of sedation, accomplished usually with intravenous drugs, plus local anesthetic injected by the surgeon. Most "MAC" anesthetics in the United States probably involve some combination of propofol, midazolam (Versed) and fentanyl. However, there are other drugs that may be used, especially in other countries. 

Sedation can certainly be administered without the use of midazolam, and some people find that a propofol-only technique is well tolerated. A potent opioid like fentanyl is needed to "cover" discomfort that is not entirely blocked by the local anesthetic, limit the pain of injection of the local anesthetic itself, and to provide some degree of pain relief once the procedure is over. 

A recent article in the British Journal of Anaesthesia may be helpful. It suggests that in patients with your kinds of problems usual anesthetic practice should apply, while obviously avoiding drugs which you are known to be sensitive to.