According to IRA publication 502 - http://www.irs.gov/pub/irs-pdf/p502.pdf you may deduct transportation expenses amounts paid for transportation primarily for, and essential to, medical care.
You can include out-of-pocket expenses, such as the cost of gas and oil, when you use a car for medical reasons. You cannot include depreciation, insurance, general repair, or maintenance expenses.
If you do not want to use your actual expenses, for 2006 you can use a standard rate of 18 cents a mile for use of a car for medical reasons.
You can also include parking fees and tolls. You can add these fees and tolls to your medical expenses whether you use actual expenses or use the standard mileage rate.
You can include in medical expenses amounts you pay for an autoette or a wheelchair used mainly for the relief of sickness or disability, and not just to provide transportation to and from work. The cost of operating and maintaining the autoette or wheelchair is also a medical expense.