Clinical use of pregabalin in the management of central neuropathic pain

Central neuropathic pain (central pain) is treated with antidepressants, various anticonvulsants, opioids, and cannabinoids, but in many cases treatment is insufficient and associated with a range of side-effects. This review addresses a new treatment for neuropathic pain, the anticonvulsant pregabalin. We review the pharmacology, mode of action, pharmacokinetics, and safety of pregabalin as well as two randomized efficacy studies in central pain and a brief overview of efficacy in peripheral neuropathic pain. Pregabalin appears to have efficacy in treating central pain comparable to that in peripheral neuropathic pain as well as efficacy of other recommended drugs for central pain. Pregabalin also improves disturbed sleep and anxiety. Pregabalin is well tolerated; the most common side-effects are somnolence, dizziness, ataxia, and weight gain. Pregabalin is suitable for patients on multiple drugs although there may be additive CNS-related side-effects. Thus, pregabalin has a primary role in central pain patients.     

Pregabalin: a new antiepileptic drug for refractory epilepsy.

Pregabalin is a recently licensed and marketed antiepileptic drug for use as adjunctive treatment of partial epilepsy. It acts at presynaptic calcium channels, modulating neurotransmitter release in the CNS, properties it shares with gabapentin. Its clinical development over the past decade has included its use in the treatment of neuropathic pain, and generalized anxiety disorder, in addition to epilepsy. Three multi-centre randomised, double-blind, placebo-controlled trials enrolling patients with refractory partial epilepsy have demonstrated an antiepileptic effect of pregabalin against placebo, as adjunctive therapy, with 31-51% of patients showing a 50% reduction in seizure frequency. Adverse effects were dose related, the commonest being somnolence, dizziness, and ataxia. Weight gain was seen in 14% of patients on the highest dose of 600 mg/day. Around 9000 people have been exposed to pregabalin in its development for all indications. No idiosyncratic reactions have been described to date. Pregabalin may be a useful addition in the treatment of refractory partial epilepsy. As with all new AEDs long-term follow up and post marketing surveillance is required.     

Pregabalin in the treatment of post‐traumatic peripheral neuropathic pain: a randomized double‐blind trial

Background: Pregabalin is effective in the treatment of peripheral and central neuropathic pain. This study evaluated pregabalin in the treatment of post‐traumatic peripheral neuropathic pain (including post‐surgical). Methods: Patients with a pain score ≥4 (0–10 scale) were randomized and treated with either flexible‐dose pregabalin 150–600 mg/day (n = 127) or placebo (n = 127) in an 8‐week double‐blind treatment period preceded by a 2‐week placebo run‐in. Results: Pregabalin was associated with a significantly greater improvement in the mean end‐point pain score vs. placebo; mean treatment difference was ?0.62 (95% CI ?1.09 to ?0.15) (P = 0.01). The average pregabalin dose at end‐point was ～326 mg/day. Pregabalin was also associated with significant improvements from baseline in pain‐related sleep interference, and the Medical Outcomes Study sleep scale sleep problems index and sleep disturbance subscale (all P < 0.001). In the all‐patient group (ITT), pregabalin was associated with a statistically significant improvement in the Hospital Anxiety and Depression Scale anxiety subscale (P < 0.05). In total, 29% of patients had moderate/severe baseline anxiety; treatment with pregabalin in this subset did not significantly improve anxiety. More patients reported global improvement at end‐point with pregabalin than with placebo (68% vs. 43%; overall P < 0.01). Adverse events led to discontinuation of 20% of patients from pregabalin and 7% from placebo. Mild or moderate dizziness and somnolence were the most common adverse events in the pregabalin group. Conclusion: Flexible‐dose pregabalin 150–600 mg/day was effective in relieving neuropathic pain, improving disturbed sleep, improving overall patient status, and was generally well tolerated in patients with post‐traumatic peripheral neuropathic pain.     

Pregabalin for treatment of generalized anxiety disorder: a 4-week, multicenter, double-blind, placebo-controlled trial of pregabalin and alprazolam

BACKGROUND: Pregabalin inhibits release of excess excitatory neurotransmitters, presumably by binding to the alpha2-delta subunit protein of widely distributed voltage-dependent calcium channels in the brain and spinal cord. OBJECTIVE: To assess the anxiolytic efficacy of pregabalin in patients with generalized anxiety disorder. DESIGN: Double-blind, placebo-controlled, active-comparator trial. Patients were randomized to 4 weeks of treatment with pregabalin, 300 mg/d (n = 91), 450 mg/d (n = 90), or 600 mg/d (n = 89); alprazolam, 1.5 mg/d (n = 93); or placebo (n = 91). SETTING: Psychiatry research and clinic settings. PATIENTS: Outpatients meeting the DSM-IV criteria for generalized anxiety disorder, with a baseline Hamilton Anxiety Rating Scale (HAM-A) total score of 20 or greater. MAIN OUTCOME MEASURES: Change from baseline to end point in total HAM-A score in the pregabalin and alprazolam groups compared with the placebo group. The end point response criterion was 50% or greater reduction in the HAM-A total score. RESULTS: Pregabalin and alprazolam produced a significantly greater reduction in mean +/- SE HAM-A total score at last-observation-carried-forward end point compared with placebo (-8.4 +/- 0.8): pregabalin, 300 mg (-12.2 +/- 0.8, P<.001), 450 mg (-11.0 +/- 0.8, P = .02), and 600 mg (-11.8 +/- 0.8, P = .002), and alprazolam (-10.9 +/- 0.8, P = .02). By week 1 and at last-observation-carried-forward end point, the 3 pregabalin groups and the alprazolam group had significantly (P<.01) improved HAM-A psychic anxiety symptoms compared with the placebo group. Compared with the placebo group, HAM-A somatic anxiety symptoms were also significantly (P<.02) improved by the 300- and 600-mg pregabalin groups, but not by the 450-mg pregabalin (week 1, P = .06; week 4, P = .32) and the alprazolam groups (week 1, P = .21; week 4, P = .15). Of the 5 treatment groups, the 300-mg pregabalin group was the only medication group that differed statistically in global improvement at treatment end point not only from the placebo group but also from the alprazolam group. CONCLUSION: Pregabalin was significantly more efficacious than placebo for the treatment of psychic and somatic symptoms of generalized anxiety disorder and was well tolerated by most study patients.     

Pregabalin as adjunctive therapy for partial epilepsy: An audit study in 96 patients from the South East of England

IntroductionPregabalin (PGB) was licensed in the EU in 2004 as an adjunctive therapy in partial epilepsy. It is also licensed for neuropathic pain and generalised anxiety.AimsTo identify the clinical usefulness and side effects of add-on PGB in out-patient epilepsy clinics.MethodsWe performed an audit on 96 consecutive patients (44 male) prescribed PGB for refractory epilepsy. Mean follow-up, for those who remained on PGB, was 23 months (range 12–39 months).ResultsFifty patients remained on PGB, 37 of whom reported clear improvement in seizure frequency. Among these 37 patients, 1 was seizure free for 15 months; 29 had a seizure reduction of >50%; and 7 improved by <50%. Eight patients reported a decrease in seizure severity without change in seizure frequency. Nine patients reported an incidental improvement in anxiety.Side effects were reported by 25 patients out of the 50 patients still on treatment: 12 reported drowsiness or tiredness, 8 weight gain, 7 dizziness, 2 headache, 2 cognitive side effects, 1 irritability, 1 itchiness, 1 anxiety, and 1 transient rash.Among the 46 patients who discontinued treatment, 9 had worsening of seizure frequency, 27 lack of efficacy and 9 intolerable side effects necessitating withdrawal (4 dizziness or drowsiness, 2 weight gain, 1 peripheral oedema, 1 pain in arms and legs, 1 irritability and cognitive side effects). One patient had a seizure related death (probably drowning) within 1 month of starting PGB.ConclusionPregabalin seems to be an effective and well-tolerated anti-epileptic drug when used as add-on treatment in patients with refractory partial epilepsy.     

Pharmacology and mechanism of action of pregabalin: the calcium channel alpha2-delta (alpha2-delta) subunit as a target for antiepileptic drug discovery

Pregabalin (Lyrica) is a new antiepileptic drug that is active in animal seizure models. Pregabalin is approved in US and Europe for adjunctive therapy of partial seizures in adults, and also has been approved for the treatment of pain from diabetic neuropathy or post-herpetic neuralgia in adults. Recently, it has been approved for treatment of anxiety disorders in Europe. Pregabalin is structurally related to the antiepileptic drug gabapentin and the site of action of both drugs is similar, the alpha2-delta (alpha2-delta) protein, an auxiliary subunit of voltage-gated calcium channels. Pregabalin subtly reduces the synaptic release of several neurotransmitters, apparently by binding to alpha2-delta subunits, and possibly accounting for its actions in vivo to reduce neuronal excitability and seizures. Several studies indicate that the pharmacology of pregabalin requires binding to alpha2-delta subunits, including structure-activity analyses of compounds binding to alpha2-delta subunits and pharmacology in mice deficient in binding at the alpha2-delta Type 1 protein. The preclinical findings to date are consistent with a mechanism that may entail reduction of abnormal neuronal excitability through reduced neurotransmitter release. This review addresses the preclinical pharmacology of pregabalin, and also the biology of the high affinity binding site, and presumed site of action.     

Efficacy and safety of pregabalin in the treatment of generalized anxiety disorder: a 6-week, multicenter, randomized, double-blind, placebo-controlled comparison of pregabalin and venlafaxine

OBJECTIVE: Pregabalin has demonstrated robust, rapid efficacy in reducing symptoms of generalized anxiety disorder (GAD) in 4 placebo-controlled clinical trials. The current study compared the efficacy and safety of pregabalin and venlafaxine in patients diagnosed with moderate to severe GAD. METHOD: The study was conducted from December 21, 1999, to July 31, 2001. Outpatients (N = 421) in primary care or psychiatry settings meeting DSM-IV criteria for GAD were randomly assigned to 6 weeks of double-blind treatment with pregabalin 400 or 600 mg/day, venlafaxine 75 mg/day, or placebo. The primary analysis was change in Hamilton Rating Scale for Anxiety (HAM-A) total score from baseline to last-observation-carried-forward (LOCF) endpoint. Secondary analyses included the change in HAM-A psychic (emotional) and somatic (physical) factor scores, significant improvement at week 1, and week 1 improvement sustained at every visit through endpoint. RESULTS: Pregabalin at both dosages (400 mg/day, p = .008; 600 mg/day, p = .03) and venlafaxine (p = .03) produced significantly-greater improvement in HAM-A total score at LOCF endpoint than did placebo. Only the pregabalin 400-mg/day treatment group experienced significant improvement in all a priori primary and secondary efficacy measures. Pregabalin in both dosage treatment groups (400 mg/day, p < .01; 600 mg/day, p < .001) significantly improved HAM-A total score at week 1, with significant improvement through LOCF endpoint. Statistically significant improvement began at week 2 for venlafaxine. Discontinuation rates due to associated adverse events were greatest in the venlafaxine treatment group: venlafaxine, 20.4%; pregabalin 400 mg/day, 6.2%; pregabalin 600 mg/day, 13.6%; placebo, 9.9%. CONCLUSION: Pregabalin was safe, well tolerated, and rapidly efficacious across the physical-somatic as well as the emotional symptoms of GAD in the majority of patients studied in primary care and psychiatric settings.     

Pregabalin for the treatment of generalized anxiety disorder: a novel pharmacologic intervention

Pregabalin is the first anxiolytic pharmacologic alternative for the treatment of generalized anxiety disorder (GAD) to be introduced in more than 10 years. GAD is a significant psychiatric condition with lifetime prevalence rates ranging between 5.7 and 6.4%. It causes significant impairment in quality of life and functional abilities equivalent to those associated with major depression. Randomized, controlled trials confirm that pregabalin is superior to placebo and comparable with lorazepam, alprazolam and venlafaxine for the treatment of patients with moderate-to-severe GAD. The onset of anxiolytic activity for pregabalin is apparent within 1 week following initiation of treatment, which is more rapid than that obtained with paroxetine and venlafaxine. Additionally, pregabalin has demonstrated potential for the prevention of relapse of GAD. Recently, the efficacy, safety and tolerability of pregabalin were also shown in a placebo-controlled study with elderly patients. Safety and tolerability profiles are favorable, with transient dizziness and somnolence of mild-to-moderate severity being the most commonly reported adverse events. Pregabalin has minimal potential for drug-drug interactions and does not provoke a clinically significant withdrawal response. Furthermore, pregabalin has low potential for abuse and dependence, unlike other classes of medications used for the treatment of GAD. Clinicians may consider the use of pregabalin in lieu of benzodiazepines as an alternative therapy for their patients with GAD.     

Efficacy and tolerability of pregabalin in partial epilepsy

Pregabalin, the most recently approved antiepileptic drug, is a structural analog of GABA with a favorable pharmacokinetic profile. Pregabalin binds to the alpha2-delta subunit of a neuronal voltage-gated calcium channel and is believed to exert its anticonvulsant effect by modulating the release of specific neurotransmitters from hyperexcited presynaptic neurons. Animal models of epilepsy have suggested that this drug will be efficacious against partial-onset and generalized tonic-clonic seizures. Four pivotal, add-on clinical trials conducted in patients with partial-onset seizures demonstrated that pregabalin at daily doses of 150-600 mg is efficacious and associated with dose-dependent adverse events. Meta-analyses of efficacy and tolerability indicated that pregabalin is an efficacious and relatively well-tolerated antiepileptic drug.     

An open-label, add-on study of pregabalin in patients with partial seizures: A multicenter trial in Greece

Introduction

Pregabalin efficacy and safety as an adjunctive treatment for partial seizures was evaluated using an open-label, flexible-dose.

Study design

In 98 adults with refractory partial epilepsy taking 1–3 anti-epileptic drugs with ≥2 seizures during an 8-week baseline period.

Methods

Pregabalin was increased to ≤600 mg/day during a 9-week dose optimization period with dosage maintained for 12 additional weeks. Primary endpoint was the percentage change in partial seizure frequency between the 8-week baseline and 12-week observation period.

Results

Pregabalin treatment was associated with a significant reduction in partial seizure frequency: median percent change in partial seizure frequency from baseline to 12 weeks was −33% and −22% in patients with a baseline seizure frequency of ≤3 and >3 per 28 days, respectively. The 50% and 75% responder rates were 41.94% (95% CI: 31.91–51.96) and 30.11% (95% CI: 20.78–39.43), respectively. Nineteen percent of subjects were seizure-free throughout the last 12 weeks. Pregabalin administration resulted in a significant reduction in anxiety (mean reduction in Hospital Anxiety and Depression Scale scores of 1.68 units, 95% CI: −2.60 to −0.76). Most patients were much improved or very much improved on Patient Global Impression of Change (53.8%) and Clinical Global Impression of Change (53.8%). The most frequently self-reported adverse events (AEs) were mild or moderate somnolence (20.4%) and dizziness (5.1%) with a low AE discontinuation rate (5.1%).

Conclusions

The efficacy and side-effect profile of pregabalin were similar to previous pregabalin double-blind, controlled studies. Additionally, pregabalin, as an add-on treatment for partial epilepsy, exhibits significant anti-anxiety properties.     

Psychopharmakotherapeutische Ans?tze bei somatoformen St?rungen und funktionellen K?rpersyndromen

Somatoform disorders and functional body syndromes define a major, diagnostically heterogeneous group of patients with medically unexplained physical symptoms. Psychopharmacological approaches can be derived from the conceptualization of somatoform symptoms and syndromes within a biopsychosocial model. The survey presented focuses on randomized, double-blind and placebo-controlled studies. Antidepressants show a statistically and clinically relevant impact on many somatoform symptoms. In special reference to pain symptoms serotonergic and noradrenergic antidepressants seem to mediate a more favorable effect than selective serotonin reuptake inhibitors. For some functional body syndromes, e.g. irritable bowel syndrome and fibromyalgia, a major analgesic effect of antidepressants can be underlined as well. The empirical data for fibromyalgia, however, seem to be more convincing than for irritable bowel syndrome. Pregabalin holds an empirically well established position in the treatment of fibromyalgia. As yet there is no convincing psychopharmacological strategy for chronic fatigue syndrome. Probably due to the inherent relationships to anxiety, obsessive-compulsive and depressive disorders, both hypochondria and body dysmorphic disorder can be positively treated by serotonergic antidepressants as well.     

Role of pregabalin in the treatment of generalized anxiety disorder

Generalized anxiety disorder (GAD) is a common, typically persistent, and disabling condition that is often not recognised, or treated in an evidence-based manner. Current pharmacological and psychological treatment approaches have a number of drawbacks, including a delay in onset of clinical effect, varying relative efficacy against psychological or somatic symptoms of anxiety, potentially troublesome adverse effects, and discontinuation symptoms on stopping treatment. Pregabalin is a structural analog of the inhibitory neurotransmitter gamma amino butyric acid (GABA) but is thought to exert its anxiolytic effects through binding in a state-dependent manner to the alpha-2-delta sub-unit of voltage-gated calcium channels in “over-excited” pre-synaptic neurones, reducing release of excitatory neurotransmitters such as glutamate and substance P. At fixed doses of 200 mg/day or greater, it has consistent proven efficacy in acute treatment of DSM-IV-defined GAD, with some evidence of an early onset of clinical effect, and of efficacy across psychological and somatic anxiety symptom clusters. A pregabalin dosage of 450 mg/day is efficacious in the prevention of relapse. There is at present no published direct comparison with an SSRI. The current known adverse effect profile and studies in healthy volunteers together suggest that pregabalin may have some tolerability advantages over benzodiazepines and venlafaxine, at least in short-term treatment.     

Pregabalin suppresses calcium-mediated proteolysis and improves stroke outcome

Pregabalin, a Ca(2+) channel α(2)δ-subunit antagonist with analgesic and antiepileptic activity, reduced neuronal loss and improved functional outcome in a mouse model of focal ischemic stroke. Pregabalin administration (5-10mg/kg, i.p.) 30-90 min after transient middle cerebral artery occlusion/reperfusion reduced infarct volume, neuronal death in the ischemic penumbra and neurological deficits at 24h post-stroke. Pregabalin significantly decreased the amount of Ca(2+)/calpain-mediated α-spectrin proteolysis in the cerebral cortex measured at 6h post-stroke. Together with the extensive clinical experience with pregabalin for other neurological indications, our findings suggest the potential for a therapeutic benefit of pregabalin in stroke patients.     

Pregabalin-induced generalized myoclonic status epilepticus in patients with chronic pain

Pregabalin is often used for the treatment of chronic pain syndromes. We here describe two patients with chronic pain and pregabalin-induced myoclonic status epilepticus. Patients treated with pregabalin who experience sudden behavioral changes or mycloni should be investigated for this possible side effect, and pregabalin should be reduced or discontinued if myocloni or status epilepticus occurs.     

Pregabalin as add-on therapy induces REM sleep enhancement in partial epilepsy: a polysomnographic study

Background and purpose:  To evaluate the effects of pregabalin (PGB) adjunctive therapy on sleepwake cycle and daytime somnolence in adult patients affected by partial epilepsy.
Methods:  Twelve patients affected by partial epilepsy underwent a 24-h ambulatory polysomnography and a subjective evaluation of daytime somnolence by means of the Epworth Sleepiness Scale (ESS), before and after 3 months treatment with PGB.
Results:  Pregabalin therapy reduced seizures by >50% in 8 out of 12 patients. It induced a significant increase of REM sleep and a decrease of stage 2 NREM sleep (S2). A significant increase of the ESS score was observed without reaching the pathological cut-off value (mean ESS score <10). No statistical correlation between REM sleep and seizure frequency was observed.
Discussion:  Pregabalin seems to be effective and safe in partial epilepsy. The increase of REM sleep may be indicative of an improvement of nocturnal sleep quality considering the involvement of REM sleep in learning and memory processes. REM sleep enhancement may be the result of both a direct effect of PGB on sleep generators and an indirect effect due to its clinical efficacy. The increase of ESS score within normal range suggests that daytime somnolence is a minor adverse effect of PGB.     

Pregabalin augmentation of quetiapine therapy in the treatment of fibromyalgia: an open-label, prospective trial

INTRODUCTION: Quetiapine has been shown to improve fibromyalgia symptoms, especially sleep disturbance, fatigue, morning stiffness, and mental well-being, but lacks an effect on pain. The purpose of this study was to evaluate if pregabalin, which has shown antialgic activity in fibromyalgia, added to quetiapine treatment additionally improved fibromyalgia symptomatology. METHODS: This was an open-label, 12-week study. Pregabalin was administered to 19 female fibromyalgia patients at a starting dose of 75 mg/day subsequently adjusted in according to the drug's efficacy and tolerability. Outcome measures included the Fibromyalgia Impact Questionnaire (FIQ), the Pittsburgh Sleep Quality Index, the Beck Depression Inventory, the State and Trait Anxiety Inventory, and the SF-12 Health Survey. RESULTS: Data analysis was done on the Intention-To-Treat sample which included 18 patients. Pregabalin significantly improved the pain and tiredness after awakening subscales of the FIQ as well as the physical component of the SF-12. Six patients withdrew from the study, 3 because of side effects. CONCLUSIONS: Our results suggest that the use of pregabalin can be a useful augmentation strategy in fibromyalgia patients partially responding to quetiapine.     

Pregabalin drug interaction studies: lack of effect on the pharmacokinetics of carbamazepine, phenytoin, lamotrigine, and valproate in patients with partial epilepsy

PURPOSE: Pregabalin (PGB) is an alpha2-delta ligand with demonstrated efficacy in epilepsy, neuropathic pain, and anxiety disorders. PGB is highly efficacious as adjunctive therapy in patients with refractory partial seizures. METHODS: Given its efficacy as adjunctive therapy, the potential for interaction of PGB with other antiepileptic drugs (AEDs) was assessed in patients with partial epilepsy in open-label, multiple-dose studies. Patients received PGB, 600 mg/day (200 mg q8h) for 7 days, in combination with their individualized maintenance monotherapy with valproate (VPA), phenytoin (PHT), lamotrigine (LTG), or carbamazepine (CBZ). RESULTS: Trough steady-state concentrations of CBZ (and its epoxide metabolite), PHT, LTG, and VPA were unaffected by concomitant PGB administration. Likewise, PGB steady-state pharmacokinetic parameter values were similar among patients receiving CBZ, PHT, LTG, or VPA and, in general, were similar to those observed historically in healthy subjects receiving PGB alone. The PGB-AED combinations were generally well tolerated. PGB may be added to VPA, LTG, PHT, or CBZ therapy without concern for pharmacokinetic drug-drug interactions.     

Does Pregabalin Have Neuropsychotropic Effects?: A Short Perspective

Pregabalin is a newly developed synthetic gamma-aminobutyric acid (GABA) that is approved for the treatment of fibromyalgia and several neuropathy. It has been proven to show analgesic, anxiolytic, anticonvulsant and sleep enhancement effects, which could be applicable in the treatment of a variety of psychiatric disorders. There have been consistent reports that unexplained somatic symptoms (i.e., pain) may be a part of psychiatric disorders such as major depressive disorder (MDD) and anxiety disorders. Previous researches have also suggested the possible therapeutic potential of anticonvulsants as augmentation therapy or monotherapy in the treatment of mood disorders and anxiety disorders. Hence this short perspective tries to prompt and facilitate a shifting of researchers'' attention to potential neuropsychotropic drug role of pregabalin to treat a wide range of neuropsychiatric disorders.     

Willis-Ekbom disease/restless legs syndrome in patients with opioid withdrawal

IntroductionMany patients with opioid use disorder report symptoms similar to restless legs syndrome (RLS) during withdrawal. However, whether these symptoms are true RLS, their predictors and effect of treatment with pregabalin are still unknown.MethodA total of 19 consecutive patients with opioid use disorder who were admitted for detoxification were included in this study after obtaining informed consent. Information regarding addiction was noted, and they were screened for RLS every morning and evening. Patients were also asked to provide information regarding their sleep quality during the previous night. To control opioid withdrawal, they were prescribed buprenorphine. Pregabalin was prescribed to patients who developed RLS. For analysis, patients were divided in two groups: those with RLS and those without RLS.ResultsThe average age of the subjects included in this study was 30.2 (±10.4) years. Mean duration of substance abuse was 56.8 (±38.4) months. Ten patients developed symptoms of RLS. Groups with RLS and without RLS were comparable with reference to demographics, laboratory parameters, and dose of buprenorphine that was required to control withdrawal symptoms. On average, RLS appeared after 1.7 days of abstinence. Patients described their symptoms such as crawling, creeping sensation in the muscles or “just pain”. Eight out of 10 subjects reported symptoms limited to legs; however, two described similar problems in their upper limbs as well. A change in sleep pattern was observed with delayed sleep onset at night, delayed wake time in the morning, and spending a major proportion of day asleep. Pregabalin brought significant relief to the symptoms of RLS and sleep quality.ConclusionRLS during opioid withdrawal was an independent illness seen in half of the patients. It appeared to be mediated through mu-receptors, with contributions from other factors. Pregabalin improved symptoms of RLS and quality of sleep in these patients.     

Dose-response relationship of pregabalin in patients with generalized anxiety disorder. A pooled analysis of four placebo-controlled trials

BACKGROUND: Pregabalin has been evaluated in randomised clinical trials in patients with generalised anxiety disorder (GAD) in a fixed-dose design and with the Hamilton Anxiety Scale (HAM-A) as outcome measure. Four of the available six placebo-controlled trials were found acceptable for a pooled analysis of dose-response relationship. METHOD: Both the full HAM-A (14) and the six-item subscale covering the core items of GAD (HAM-A (6)) were analysed. The unbiased effect size statistic was used to evaluate the advantage of pregabalin over placebo. An effect size of 0.40 or higher was used to indicate a clinically significant effect. RESULTS: Four placebo-controlled trials running over four weeks and covering the dose range from 150 mg to 600 mg pregabalin were sufficiently homogeneous to be pooled for the analysis. Both HAM-A (6) and HAM-A (14) showed that for the dose of 150 mg pregabalin daily the effect size was clearly below 0.40. For the dose range of 200-450 mg daily, the effect sizes exceeded 0.40, with a plateau-like curve. The maximum dose of 600 mg daily did not increase effect size. On the HAM-A (14) as well as the item of sleep, effect size was generally higher, but followed the same pattern as the HAM-A (6). DISCUSSION: The dose of 150 mg pregabalin over the four weeks of the trials was found insufficient for the treatment of GAD. In the dose range of 200-450 mg daily, a clinically significant effect was obtained, although with a plateau-like curve which was not increased for the maximum dose of 600 mg daily.