Tetracycline Antibiotics

• The tetracycline antibiotics, including minocycline and doxycycline, have immunomodulatory and neuroprotective activities. They appear to decrease the passage of leukocytes across the blood-brain barrier.


• In a small trial in patients with RRMS, minocycline decreased gadolinium-enhancing activity by 50 percent over a period of six months. A subsequent 24-month trial showed a significant decrease in lesion activity and clinical status.


• A Phase III trial beginning in 2008 is studying the effect of 100 mg of oral minocycline twice daily on the conversion of CIS to a diagnosis of MS at six and 24 months.


• A study combining minocycline with Copaxone in RRMS in 40 patients showed that the combination was more effective than Copaxone alone. This was determined by disease activity, as measured by gadolinium-enhancing and T2 lesions, as well as relapse rate.


• A small Phase IV study combining doxycycline with Avonex demonstrated a statistically significant reduction of gadolinium-enhancing lesions compared with Avonex alone. A larger trial is needed to confirm these results.