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Table 3 Key recommendations for improving recruitment in trigeminal neuralgia (TN) clinical trials

From: Challenges recruiting to a proof-of-concept pharmaceutical trial for a rare disease: the trigeminal neuralgia experience

Barrier (real or perceived)


Patients with the opportunity to try study drug have to return to prior treatment at study completion

• Only true for phase II and earlier studies

• Phase III studies should be designed with the option of a long-term extension

Required discontinuation of current therapy during the trial run-in phase

• Consider permitting use of and incorporating a higher/loading dose of the study drug to offset potential reduction in exposure owing to prior/concomitant medications

• Implementation of a downtitration and uptitration algorithm of concomitant medications and study drug, respectively

Change in diagnosis from TN to other types of TN

• The TN phenotype is also known to change over time, with potential for remission [22], which could alter whether patients meet pain requirements

• Recruitment of patients with recent visits to the clinic versus database records

Only specialists are recruiting patients attending specialist clinics

• Local primary care practices could be encouraged to telephone potential patients

A nurse could administer a semistructured questionnaire to identify potential cases for referral to the specialist center

Prescreening eligibility and screening failures inconsistently captured

• Implementation of a central project management and coordination system with prescreening and screening data locks that are promptly reviewed

Patient diary too large a burden

• Patient diaries less onerous (e.g., by not requiring documentation of all individual attacks, but rather average daily pain, or not requiring documentation of each attack after a certain threshold (e.g., > 20 attacks))

Lack of time or inability to attend study visits owing to distance/mobility

• Replace some onsite visits with telephone visits

• Consider patient compensation for time loss and/or travel/dietary expenses