Background/Purpose:  Methotrexate (MTX) is the most commonly used and recommended DMARD for the treatment of RA. SC administered MTX is well absorbed and appears to overcome the problems associated with oral administration, including variable absorption and saturation of the absorption mechanism with increasing doses.

The purpose of this study was to assess the usability, label comprehension, robustness, safety, and bioavailability of SC self-administration (SA) of the prefilled MTX pen containing 0.3 mL of MTX 50 mg/mL solution (medac GmbH, Germany) in a typical population of RA patients requiring MTX treatment. 

Methods: The study population consisted of 104 patients aged 16 years or older, including newly diagnosed and MTX naïve and those switching from an oral route of administration, or those already receiving an off-label SC route of administration.

The actual use study was performed at 5 sites over a 2-week period.

Visit 1 (V1) consisted of training on the use of the device followed by an actual self-injection. Training and SA were carefully documented by a 10-item questionnaire.

Visit 2 (V2)(8-10 days after V1) consisted of a written examination for assessing patient’s retention of information and a panel of the following 4 scenario test case observations, including an actual self-injection: 1) Holding the needle in place for approximately 5 seconds, 2) Checking the window of pen to confirm MTX delivery, 3) Performing the skin pinch in preparation for self-administration, and 4) Proper disposal of pen following self-administration.

Ease of performance of each scenario was also judged by the patients. A subjective measures questionnaire was used to record patients’ impressions, difficulties, and general comments on the device.

Bioavailability was assessed in 25 patients. Stratified by body weight categories, patients were randomly assigned to either inject MTX in the abdomen or in the upper thigh.

Results:

• After training at V1, 12 patients had questions about the MTX pen, 4 patients required assistance to perform the self-injection
• At V2, 98.1% of patients scored 80% or better on their written examination
• The successful completion rates of scenarios 1 through 4 were 96.2%, 100%, 98.1%, and 100%, respectively
• For the respective test scenarios, 91.3%, 98.1%, 99%, and 100% of patients did not require any assistance
• The mean rating of easy performance for each test case scenario was 9.8 or higher on a 1 to 10 scale with 1 being very difficult and 10 being very easy
• The subjective measures questionnaire indicated that patients felt the MTX pen was easy to use and their overall impression was favorable
• After use, all the MTX pens were intact and had reliably delivered 0.3 mL MTX
• PK analysis revealed that excessive body weight (>100 kg) significantly decreased both AUC and C_max of MTX when administered SC to the abdomen
• No adverse device effects, unanticipated adverse device effects, deaths, serious adverse events, or adverse events leading to study drug discontinuation were reported

Conclusion:

The MTX pen was consistently and reliably used by the intended population with a high degree of effectiveness, patient satisfaction, and safety.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/successful-self-administration-of-methotrexate-in-rheumatoid-arthritis-patients-using-a-prefilled-autoinjector-pen/