Doxycycline

What is Doxycycline?

Doxycycline is a member of the tetracycline family of antibiotics and is recommended for the treatment of infections caused by many common microorganisms.  Most commonly, it is used as a treatment for Lyme disease and Malaria.  It functions as an antimicrobial agent by inhibiting bacterial protein synthesis.  However, like all pharmacological agents, doxycycline has a number of secondary effects.  Treating knee osteoarthritis is thought to be one such effect.  While doxycycline is a relatively safe drug, it is contraindicated for use in pregnancy and children less than eight years of age.  In addition, outdated doxycycline can cause a fatal kidney disorder known as Fanconi’s syndrome. 

Why is it indicated in the treatment of knee osteoarthritis?

The cartilage normally found in the knee serves to protect the integrity of the joint.  It acts as a shock absorber and allows for smooth gliding of the bones involved in the joint.  Over time it is possible for the cartilage to become irritated and inflamed. These processes ultimately cause degeneration of the cartilage.  Treatments for osteoarthritis focus on reducing the inflammation and preserving the cartilage in the joint.

Current researchers have postulated that the degeneration of cartilage occurs due to microscopic proteins called matrix metalloproteinases (MMPs).  There is a correlation between a decrease in knee joint space width and plasma MMP-3 concentration in obese women who suffer from osteoarthritis³.  Doxycycline has a potential regulatory effect on the activity of these MMPs, and in preliminary studies researchers found that doxycycline may slow the progression of knee osteoarthritis in obese women.  To measure the degree of cartilaginous degradation in the knee, the change in joint space width was monitored over a period of 30 months.  In patients who received 100mg doxycycline twice daily, there was a significantly lower rate of joint space narrowing compared to placebo².

What are the implications of this research?

Doxycycline looks to be very promising in its ability to slow the progression of cartilage degradation in knee osteoarthritis.  However, additional investigation is required to determine if doxycycline is effective in the prevention of knee osteoarthritis.

Authors:  Kapil Kataria, B.A., New York College of Osteopathic Medicine, Old Westbury, NY

            Elise Weiss, M.D., New York-Presbyterian Hospital, The University Hospital of Columbia and Cornell, New York, NY

References

[1] Baum, Jonathan D., et. al. Drug Charts in Basic Pharmacology.  West Chester: Medical Surveillance Inc., 1998.

[2] Brandt, KD, et. al. “Effects of doxycycline on progression of osteoarthritis: results of a randomized, placebo-controlled, double-blind trial.”  Arthritis Rheumatology. 2005 Jul; 52(7):2015-25.

[3] Lohmander, LS, et. al.  “Use of the plasma stromelysin (matrix metalloproteinase 3) concentration to predict joint space narrowing in knee osteoarthritis.”  Arthritis Rheumatology. 2005 Oct; 52(10):3160-7.