Doxycycline for Elbow Tendinopathy

: elbow tendinopathy is a common condition among athletes and the general population. It can result in significant disability and time loss from work. Despite traditional nonsurgical treatment, symptoms often persist for more than 6 months. Second-line treatments, such as platelet rich plasma injections and extracorporeal shock wave therapy, have limited evidence and are often cost-prohibitive. There remains a need for additional cost-effective nonsurgical treatment for elbow tendinopathy.

Purpose: To evaluate the feasibility of subantimicrobial -dose (SD) doxycycline to improve outcomes of nonsurgical management of elbow tendinopathy via matrix metalloproteinase (MMP) inhibition as well as evaluate if participants will be compliant to with prescribed medication and exercise treatment. Our working hypothesis is that patients with elbow tendinopathy will be receptive to treatment with SD-doxycycline and compliant with the prescribed treatment.

Methods: This study will enroll 25 otherwise healthy males and females ages 18 and up with ≥ 6 weeks of symptomatic lateral or medial elbow tendinopathy. Subjects will receive doxycycline 20 mg BID (twice a day) for 12 weeks. Usual care will also be provided with a home exercise program and a counterforce brace. The proportion of eligible patients who elect to participate in the study will be tracked as a measure of receptiveness. Biweekly logs will be collected to monitor for treatment side effects and track compliance. Patient reported outcomes will include quick Disabilities of the Arm Shoulder and Hand score (qDASH) and Patient-Rated Tennis Elbow Evaluation (PRTEE) at baseline, 4, 8, and 12 weeks. Ultrasound tendinopathy grade and grip strength will be measured at baseline and 12 weeks. Blood will be drawn to assess MMP activity and collagen production/connective tissue anabolism at baseline and 12 weeks.

Significance: This study will provide the necessary data to design a phase two-a trial of a safe, low-cost adjuvant treatment for a common condition treated by sports medicine and primary care physicians. If found to be beneficial for elbow tendinopathy, SD-doxycycline may have utility in other types of tendinopathy as well.

Inclusion criteria

• Males and females ages of 18 and up
• Atraumatic unilateral elbow pain of ≥ 6 weeks duration
• Diagnosed clinically as lateral or medial elbow tendinopathy
• Activity-related lateral or medial elbow pain
• Tenderness of the lateral or medial epicondyle
• Pain with gripping and/or resisted wrist extension with the elbow extended
• Pain with passive wrist flexion and finger with the elbow extended
• Internet access to complete electronic surveys

Exclusion criteria

• Prior surgery of the affected elbow
• Prior injection of the affected lateral or medial epicondyle or extensor tendons
• Prior extracorporeal shockwave therapy to the affected elbow
• Suspicion for radial tunnel syndrome (tenderness distal to the lateral epicondyle in the area of the supinator muscle dorsally, pain with resisted supination with the elbow extended, and/or weakness of the extensor digitorum communis)
• Separate upper extremity injury or condition that would interfere with full participation in the home exercise program
• Fluoroquinolone-associated tendinopathy
• Ligamentous laxity on exam
• Evidence of osteoarthritis or osteochondral lesion on radiographs
• Autoimmune condition
• Pregnant, intend to become pregnant, or breastfeeding
• Premenopausal women who are not using contraception
• Allergy to doxycycline or other tetracyclines
• Current esophagitis or peptic ulcer disease
• Current use of medication for which there is a drug interaction with doxycycline
• Who do not speak English