I have run 5 miles three time a week for 14 years but within the last 6mo have had terrible pain in my lower legs. Anchle joints, calf pain and shin splints. I have tried various forms of stretching, rest, pain relievers, new shoes, the standard runner stuff but the symptoms persist. It must be very frustrating for you to have all of these unpleasant symptoms-especially since you've been a runner for 14 years.
Anemia can cause muscle cramping when inadequate oxygenation of muscle tissue occurs.
The fact that your joints and shins are also bothering you tells me that there may be more to the problem than the possibility of anemia. A referral to a doctor who specializes in sports medicine, might be a good idea. Circulatory impairment to the lower legs can also cause many of the symptoms you've described. I'm going to send e-mail to my colleagues to see if they are encountering this problem in any of their patients on combination therapy. Let us know about your progress.