Efficacy and Safety Study of Pregabalin in the Treatment of Pain on Walking in Patients With Diabetic Peripheral Neuropathy (DPN)

The daily pain diary consisted of an 11-point numeric scale ranging from 0 ("no pain") to 10 ("worst possible pain"). Participants described their pain during the past 24 hours by having chosen the appropriate number between 0 and 10. Self-assessment was performed daily each evening before bedtime (6.00 pm to midnight) on the telephone via Interactive Voice Recognition System (IVRS). The endpoint mean pain score was defined as the mean of the last 7 daily diary pain ratings while taking study medication in each treatment period - Period 1 and Period 2, respectively. A rating of 1 - 3 was considered as mild pain; 4 - 6 as moderate pain; and 7 - 10 as severe pain.

The post-test DPN pain on walking NRS consisted of an 11-point numeric scale ranging from 0 ("no pain") to 10 ("worst possible pain"). Participants described their DPN pain in their legs and/or feet while walking during the 50-foot walk test by choosing the appropriate number between 0 and 10. The post-test DPN pain on walking NRS was completed by the participant using paper-pen administration immediately after completing the 50-foot walk test at the end of each treatment period - Period 1 and Period 2, respectively. A rating of 1 - 3 was considered as mild pain; 4 - 6 as moderate pain; and 7 - 10 as severe pain.

The daily pain diary consisted of an 11-point numeric scale ranging from 0 ("no pain") to 10 ("worst possible pain"). Participants described their pain during the past 24 hours by having chosen the appropriate number between 0 and 10. Self-assessment was performed daily each evening before bedtime (6.00 pm to midnight) on the telephone via IVRS. The endpoint mean pain score was defined as the mean of the last 7 daily diary pain ratings while taking study medication in each treatment period - Period 1 and Period 2, respectively. A rating of 1 - 3 was considered as mild pain; 4 - 6 as moderate pain; and 7 - 10 as severe pain.

The daily pain diary consisted of an 11-point numeric scale ranging from 0 ("no pain") to 10 ("worst possible pain"). Participants described their pain during the past 24 hours by having chosen the appropriate number between 0 and 10. Self-assessment was performed daily each evening before bedtime (6.00 pm to midnight) on the telephone via IVRS. The endpoint mean pain score was defined as the mean of the last 7 daily diary pain ratings while taking study medication in each treatment period - Period 1 and Period 2, respectively. A rating of 1 - 3 was considered as mild pain; 4 - 6 as moderate pain; and 7 - 10 as severe pain.

The BPI-sf is a self-administered questionnaire developed to assess the severity of pain and the impact of pain on daily functions during a 24 hour period prior to evaluation. The BPI-sf consists of 5 questions: 4 items measure pain (0: no pain; 10: worst pain possible) at its "worst, "least", "average", and "now" (current pain) on an 11-point scale. Scores range from 0 - 40 with higher scores indicating greater pain severity. Another item, containing 7 sub-questions, evaluates the level of interference of pain on daily functioning (general activity, walking, work ability, mood, enjoyment of life, relations with other people, and sleep) on 11-point scales (0: does not interfere; 10: completely interferes). Scores range from 0 - 70 with higher scores indicating greater interference.

The BPI-sf is a self-administered questionnaire developed to assess the severity of pain and the impact of pain on daily functions during a 24 hour period prior to evaluation. The BPI-sf consists of 5 questions: 4 items measure pain (0: no pain; 10: worst pain possible) at its "worst, "least", "average", and "now" (current pain) on an 11-point scale. Scores range from 0 - 40 with higher scores indicating greater pain severity. Another item, containing 7 sub-questions, evaluates the level of interference of pain on daily functioning (general activity, walking, work ability, mood, enjoyment of life, relations with other people, and sleep) on 11-point scales (0: does not interfere; 10: completely interferes). Scores range from 0 - 70 with higher scores indicating greater interference.

The BPI-sf is a self-administered questionnaire developed to assess the severity of pain and the impact of pain on daily functions during a 24 hour period prior to evaluation. The BPI-sf consists of 5 questions: 4 items measure pain on an 11-point scale. Scores range from 0 - 40 with higher scores indicating greater pain severity. Another item, containing 7 sub-questions, evaluates the level of interference of pain on daily functioning (general activity, walking, work ability, mood, enjoyment of life, relations with other people, and sleep) on 11-point scales (0: does not interfere; 10: completely interferes). Scores range from 0 - 70 with higher scores indicating greater interference. The sub-score pain interference with walking ability was evaluated, as it was considered to be the most relevant in the context of this study.

Actigraphy data which measured steps and daytime activity during waking hours were assessed for the last 7 days at Baseline, Visit 6, and Visit 11. Activity counts are the units of motion. It is equal to the sum of peak accelerations each second during the epoch (60 seconds). Total activity counts per day is the sum of the activity counts for each epoch (60 seconds) during the "day" (non-sleep period). Actigraphy was performed with an accelerometer that was worn on the hip during the waking hours. It was programmed to record movements while the device was being worn.

Actigraphy data which measured steps and daytime activity during waking hours were assessed for the last 7 days at Baseline, Visit 6, and Visit 11. The participants were instructed to wear the device on their hip during the waking hours.

The Walk-12 is a self-administered questionnaire that assesses the impact of the participant's diabetic neuropathy over the past 2 weeks on parameters associated with walking (12 questions) based on a 5-point scale (from not at all to extremely). The total score is the sum of scores from the 12 questions, which then gets transferred to a 0-100 scale with higher scores indicating greater impairment

Norfolk QOL-DN is a 35-item participant-rated questionnaire used to assess impact of diabetic neuropathy on the quality of life of participants with diabetic neuropathy. All symptoms (1 - 7) are scored as either 1 or 0, indicating presence or absence of the symptom. With the exception of questions 31 and 32, the other items are scored according to the 5-point Likert Scale (0 - 4, "no problem" to "severe problem"). In question 31, "good", the middle item, is scored as 0, "very good" as -1, "excellent" as -2, "fair" as 1, and "poor" as 2. In question 32, "about the same", the middle item, is scored as 0, "somewhat better" as -1, "much better" as -2, "somewhat worse" as 1, and "much worse" as 2. TQOL score should be summed as follow: sum (Σ) (1 - 7, 8 - 35). The scales and subscales are calculated without weighting of any kind, and reported as the integer sum of the listed questionnaire items.

Norfolk QOL-DN is a 35-item participant-rated questionnaire used to assess impact of diabetic neuropathy on the quality of life of participants with diabetic neuropathy. All symptoms (1 - 7) are scored as either 1 or 0, indicating presence or absence of the symptom. With the exception of questions 31 and 32, the other items are scored according to the 5-point Likert Scale (0 - 4, "no problem" to "severe problem"). In question 31, "good", the middle item, is scored as 0, "very good" as -1, "excellent" as -2, "fair" as 1, and "poor" as 2. In question 32, "about the same", the middle item, is scored as 0, "somewhat better" as -1, "much better" as -2, "somewhat worse" as 1, and "much worse" as 2. The symptoms domain score should be summed as follow: Σ(1 - 7, 9). The scales and subscales are calculated without weighting of any kind, and reported as the integer sum of the listed questionnaire items.

Norfolk QOL-DN is a 35-item participant-rated questionnaire used to assess impact of diabetic neuropathy on the quality of life of participants with diabetic neuropathy. All symptoms (1 - 7) are scored as either 1 or 0, indicating presence or absence of the symptom. With the exception of questions 31 and 32, the other items are scored according to the 5-point Likert Scale (0 - 4, "no problem" to "severe problem"). In question 31, "good", the middle item, is scored as 0, "very good" as -1, "excellent" as -2, "fair" as 1, and "poor" as 2. In question 32, "about the same", the middle item, is scored as 0, "somewhat better" as -1, "much better" as -2, "somewhat worse" as 1, and "much worse" as 2. The activities of daily living domain score should be summed as follow: Σ(12, 22, 23, 25, 26). The scales and subscales are calculated without weighting of any kind, and reported as the integer sum of the listed questionnaire items.

Norfolk QOL-DN is a 35-item participant-rated questionnaire used to assess impact of diabetic neuropathy on the quality of life of participants with diabetic neuropathy. All symptoms (1 - 7) are scored as either 1 or 0, indicating presence or absence of the symptom. With the exception of questions 31 and 32, the other items are scored according to the 5-point Likert Scale (0 - 4, "no problem" to "severe problem"). In question 31, "good", the middle item, is scored as 0, "very good" as -1, "excellent" as -2, "fair" as 1, and "poor" as 2. In question 32, "about the same", the middle item, is scored as 0, "somewhat better" as -1, "much better" as -2, "somewhat worse" as 1, and "much worse" as 2. The physical functioning / large fiber domain score should be summed as follow: Σ(8, 11, 13 - 15, 24, 27 - 35). The scales and subscales are calculated without weighting of any kind, and reported as the integer sum of the listed questionnaire items.

Norfolk QOL-DN is a 35-item participant-rated questionnaire used to assess impact of diabetic neuropathy on the quality of life of participants with diabetic neuropathy. All symptoms (1 - 7) are scored as either 1 or 0, indicating presence or absence of the symptom. With the exception of questions 31 and 32, the other items are scored according to the 5-point Likert Scale (0 - 4, "no problem" to "severe problem"). In question 31, "good", the middle item, is scored as 0, "very good" as -1, "excellent" as -2, "fair" as 1, and "poor" as 2. In question 32, "about the same", the middle item, is scored as 0, "somewhat better" as -1, "much better" as -2, "somewhat worse" as 1, and "much worse" as 2. The small fiber domain score should be summed as follow: Σ(10, 16, 17, 18). The scales and subscales are calculated without weighting of any kind, and reported as the integer sum of the listed questionnaire items.

Norfolk QOL-DN is a 35-item participant-rated questionnaire used to assess impact of diabetic neuropathy on the quality of life of participants with diabetic neuropathy. All symptoms (1 - 7) are scored as either 1 or 0, indicating presence or absence of the symptom. With the exception of questions 31 and 32, the other items are scored according to the 5-point Likert Scale (0 - 4, "no problem" to "severe problem"). In question 31, "good", the middle item, is scored as 0, "very good" as -1, "excellent" as -2, "fair" as 1, and "poor" as 2. In question 32, "about the same", the middle item, is scored as 0, "somewhat better" as -1, "much better" as -2, "somewhat worse" as 1, and "much worse" as 2. The autonomic domain score should be summed as follow: Σ(19, 20, 21). The scales and subscales are calculated without weighting of any kind, and reported as the integer sum of the listed questionnaire items.

The PGIC is a participant-rated instrument that measures the participant's assessment of change in his/her overall status on a scale ranging from 1 (very much improved) to 7 (very much worse). Original scores (OS; 7 different scores) and categorized scores (CS; 4 different scores) were provided. Categorized scores were very much improved (consisting of very much improved and much improved); any improvement (consisting of very much improved, much improved, and minimally improved); no change (consisting of no change); and any worsening (consisting of minimally worse, much worse, and very much worse). Due to the crossover design, PGIC was analyzed at the end of period 1 (V6).

The daily sleep diary consists of an 11-point numeric rating scale with which the participant rates how painful DPN pain has interfered with their sleep during the past 24 hours. Zero indicates "does not interfere with sleep" and 10 indicates "completely interferes (unable to sleep due to pain)". Self-assessment was performed daily in the evening before bedtime on a telephone via IVRS (time window for completion between 6.00 pm to midnight) after completion of the daily pain diary.

The Hospital Anxiety and Depression Scale (HADS) is a 14-item self-administered questionnaire that consists of 2 scales, one measuring anxiety (HADS-A), and the other measuring depression (HADS-D). Each subscale consists of 7 statements and the participant responds as to how each item applies to him/her over the past week on 4-point response scale. Separate scores are calculated for anxiety and depression and a score (ranging from 0 to 21) is obtained for each subscale. The higher the score, the more severe the anxiety or depression.

The HADS is a 14-item self-administered questionnaire that consists of 2 scales, one measuring anxiety (HADS-A), and the other measuring depression (HADS-D). Each subscale consists of 7 statements and the participant responds as to how each item applies to him/her over the past week on 4-point response scale. Separate scores are calculated for anxiety and depression and a score (ranging from 0 to 21) is obtained for each subscale. The higher the score, the more severe the anxiety or depression.

The EQ-5D describes participant's health status based on 5 attributes producing an 5 digit index score. The 5 dimensions are: mobility, self-care, usual activities, pain / discomfort, and anxiety / depression. Dolan 1997 advised how to transfer this index score to a single score for clinical trials, a revised single index was published in 2001. The index uses general population weighted estimates for various health states. In general, the range of the single index tends to vary between 0 = death and 1 = perfect health and there are some states that have been rated by the general population to be worse than death which may result in numbers below 0.