Review authors carried out data extraction and quality assessment of the included trials independently and in duplicate. We discussed discrepancies until we reached consensus. We consulted a third review author in cases of persistent disagreement. We contacted authors of primary studies when necessary.
MAIN RESULTS: We identified 18 potentially relevant RCTs, but only seven met the inclusion criteria. All studies had a small number of participants, ranging from seven to 16 people per study and had a cross-over design. Three studies were of low risk of bias, while four were of uncertain risk.
Amitriptyline (three studies),
bromocriptine (one study),
clonidine (one study),
propranolol (one study),
levodopa (Prolopa®) (one study) and
tryptophan (one study) were compared with placebo. Studies evaluating
bromocriptine,
clonidine,
propranolol and
levodopa reported our primary outcome of indices of
bruxism motor activity.Results were imprecise and consistent with benefit, no difference or harm. These were the specific findings for each of the drugs according to specific outcomes: 1.
Amitriptyline versus placebo for masseteric electromyography (EMG) activity per minute: standardized mean difference (SMD) -0.28 (95% confidence interval (CI) -0.91 to 0.34; P value = 0.37), 2.
bromocriptine versus placebo for
bruxism episodes per hour: mean difference (MD) 0.60 (95% CI -2.93 to 4.13),
bruxism bursts per hour: MD -2.00 (95% CI -53.47 to 49.47),
bruxism bursts per episode: MD 0.50 (95% CI -1.85 to 2.85) or number of episodes with grinding noise: MD 2.40 (95% CI -24.00 to 28.80), 3.
clonidine versus placebo for number of
bruxism episodes per hour: MD -2.41 (95% CI -4.84 to 0.02), 4.
propranolol versus placebo for the number of
bruxism episodes per hour: MD 1.16 (95% CI -1.89 to 4.21), 5.
L-tryptophan versus placebo for masseteric EMG activity per second: SMD 0.08 (95% CI -0.90 to 1.06) and 6.
levodopa versus placebo for
bruxism episodes per hour of sleep: MD -1.47 (95% CI -3.64 to 0.70), for
bruxism bursts per episode: MD 0.06 (95% CI -2.47 to 2.59).We combined several secondary outcomes (sleep duration, masseteric EMG activity per minute and
pain intensity) in a meta-analysis for comparison of
amitriptyline with placebo. The results for most comparisons were uncertain because of statistical imprecision. One study reported that
clonidine reduced rapid eye movement (REM) sleep stage and increased the second stage of sleep. However, results for other sleep-related outcomes with
clonidine were uncertain. Adverse effects were frequent in people who took
amitriptyline (5/10 had drowsiness, difficulty awakening in the morning,
insomnia or
xerostomia compared with 0/10 in the placebo group), as well as in people who received
propranolol (7/16 had moderate-to-severe
xerostomia compare with 2/16 in the placebo group).
Clonidine was associated with prolonged morning
hypotension in three of 16 participants. The use of preventive medication avoided any adverse effects in people treated with
levodopa and
bromocriptine.
AUTHORS' CONCLUSIONS: