What of hemodialysis-associated itching? A double-blind, placebo-controlled study crossover

What is the role of gabapentin in the
management of hemodialysis-associated itching?

 

A double-blind,
placebo-controlled study crossover study was performed to see the effectiveness
of gabapentin on patients with uremic pruritus. Twenty-five adult patients (14
men and 11 women) were enrolled in the study. The patients were 18 years old or
above. The patients were on hemodialysis, which was used for 4-5 hours three
times a week with a polysuphone dialyzer. All patients in this study had
histories of pruritus of greater than 8 weeks duration and none of them had
dermatological, liver or metabolic disease associated with pruritus. The
patients used a visual analogue scale to rate the level of their pruritus daily.
The scale had a horizontal line marked 0 (non-pruritus) to 10 (severe pruritus).
During the experiment, the patients received gabapentin therapy for 4 weeks
followed by 4 weeks of placebo or 4 weeks of placebo followed by gabapentin for
4 weeks. There was a week washout period between each phases. The patients had
to submit their pruritus scores the week before the trial, the active treatment
phase, the placebo phase, and the intervening washout period. At the end of hemodialysis
sessions, 300 mg Gabapentin or placebo was given to patients three times a
week.  The experimenters used the mean of
the score to determine the actual score of each period. 1

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The data given
before and after the experiment were given and analyzed. The mean pruritus
score prior to the experiment came out to be 8.40.94 (range:
7-10). The score decreased to 7.6range: 2-10;
P=0.098) after placebo administration. The mean pruritus score returned to the
baseline levels (7.91.1) after the
1-week washout period. The mean score decreased to 1.21.8 (range 0-8;
P=0.0001) after gabapentin administration. During the experiment, the patients
experienced mild to moderate side effects such as somnolence, dizziness, and
fatigue from taking gabapentin. Gabapentin was proven to be an effective
therapy for uremic pruritus in hemodialysis patients. Not only this study had
found evidence that gabapentin can have a positive effect on patients with hemodialysis
itching, there was another study suggested that gabapentin could be used as a
safe and effective treatment for uremic itch.  

Another study
was done as a double blind, placebo-controlled trial. Thirty-four adult
patients (16 males and 18 females) participated in this study. The mean age of
these patients was 62 years old. Patients with skin disease other than uremic
pruritus were excluded from the study. During the experiment, the patients were
randomly assigned to either gabapentin 400 mg or placebo group. The placebo was
an emptied gabapentin capsule filled with flour. The study involved with the
patients receiving four weeks of treatment with either gabapentin 400 mg or
placebo administered twice weekly after hemodialysis sessions. Similar to the first
study, a visual analogue was used for patients to record their pruritus scores.
The pruritus scores were compared between the group receiving Gabapentin 400 mg
and the placebo group. After the four weeks, they found that the mean pruritus
score decreased in both groups. Before the experiment, the experimenters
collected the pain scores from the patients. The mean pruritus score at
baseline was 7.2 2.3 (range
3-10). As a result, the pruritus mean in the gabapentin group was 6.72.6 and placebo
group was 1.51.8, (p < 0.001) after the four weeks of treatment. The mean in pruritus scores after the study period was compared between two groups with two-sample independent t-tests, and the statistical analysis was performed using SPSS version 11.0 software. This study supports the idea that gabapentin can effectively alleviate pruritus in uremic patients.2 After analyzing these articles, these two studies showed similar experimental design. For instance, both studies were double-blinded and they compared the effectiveness between placebo and gabapentin. In addition, both studies used visual analogue for patients to record their pruritus scores. The differences would be that the second study had a larger sample size, used a higher dose of gabapentin (400 mg), and was a shorter experiment (4 weeks). After reviewing these studies, there were some strengths and weaknesses of these articles that can be taken into consideration. For instance, one of the strengths would be that the first study was a random, double-blinded, crossover study. This study method reduced the chance of bias. In addition, the duration of the experiment was reasonable. The idea of having the patients be on four weeks of gabapentin followed by four weeks of placebo or vice versa showed a difference the effectiveness between the placebo and gabapentin. Nevertheless, one of the weaknesses would be that the first article did not provide enough information on graphs. For example, Figure 1 did not show a clear comparison between the visual analogue scale scores. The graph should have a more descriptive legend. The graph can be better represented with a bar graph instead of a plot graph. Another factor that limited this study was that the pruritus scores were measured once a day and the scores were only subjective indications of the level of itching.1 Similar to the first study, the second study was also a double blinded, placebo-controlled study which reduced bias. A weakness would be that the pruritus scores were also measured based on patients' sense of itchiness. This measurement is subjective because the level of itchiness may be different for other people.2 There were studies that demonstrated that gabapentin can alleviate pruritus by comparing Gabapentin and placebo. Overall, the two studies that were mentioned showed that gabapentin had a greater effect on pruritus than a placebo drug. 

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