Emerging drugs for restless legs syndrome

Cross-Sectional Design: Link Between Parkinson's Pain and Restless Leg Syndrome

OBJECTIVE

Prior research suggests that restless leg syndrome (RLS) is prevalent in Parkinson's disease (PD) with insufficient evidence to support the relationship between RLS, PD, and pain. This study explored the relationship between pain in PD patients and its association with the prevalence and severity of RLS.

METHOD

127 PD patients were assessed for PD and RLS using the U.K. Brain bank Criteria and the Restless Leg Syndrome diagnostic criteria, respectively. These patients were also assessed for pain perception and interference using the Brief Pain Inventory.

RESULTS

The results demonstrated Parkinson's disease patients who reported pain scored 23 more Restless Leg Syndrome prevalence points (p < 0.05), and 8.5 counts higher for Restless Leg Syndrome severity (p < 0.05) compared to the group of Parkinson's disease patients denying pain.

DISCUSSION

The presence of pain in PD patients indicated a higher RLS prevalence and an increased RLS severity. This finding suggests patients suffering from pain interference may experience more severe RLS symptoms. This demonstrates an inextricable link and association between pain in PD patients and RLS. Further robust investigations are required to elucidate any potential causative links, which can inform more holistic treatment principles.

The restless legs syndrome: is it more than that?

The restless legs syndrome is not only common and frequently unrecognized but research has revealed that the limb symptoms are only part of the clinical picture. Abnormalities of dopamine availability in the CNS have been demonstrated and suggest new approaches to treatment.

A randomized, double-blind, 6-week, dose-ranging study of pregabalin in patients with restless legs syndrome

OBJECTIVE

This study evaluated the dose-related efficacy and safety of pregabalin in patients with idiopathic restless legs syndrome (RLS).

METHODS

This six-arm, double-blind, placebo-controlled, dose-response study randomized patients (N=137) with moderate-to-severe idiopathic RLS in an equal ratio to placebo or pregabalin 50, 100, 150, 300, or 450 mg/day. The dose-response was characterized using an exponential decay model, which estimates the maximal effect (E(max)) for the primary endpoint, the change in the International Restless Legs Study Group Rating Scale (IRLS) total score from baseline to week 6 of treatment. Secondary outcomes included Clinical Global Impressions-Improvement Scale (CGI-I) responders, sleep assessments, and safety.

RESULTS

The separation of treatment effect between placebo and pregabalin began to emerge starting at week 1 which continued and increased through week 6 for all dose groups. The IRLS total score for pregabalin was dose dependent and well characterized for change from baseline at week 6. The model estimated 50% (ED(50)) and 90% (ED(90)) of the maximal effect in reducing RLS symptoms that occurred at pregabalin doses of 37.3 and 123.9 mg/day, respectively. A higher proportion of CGI-I responders was observed at the two highest doses of pregabalin (300 and 450 mg/day) versus placebo. Dizziness and somnolence were the most common adverse events and appeared to be dose-related.

CONCLUSIONS

In this 6-week phase 2b study, pregabalin reduced RLS symptoms in patients with moderate-to-severe idiopathic RLS. The symptom reduction at week 6 was dose-dependent with 123.9 mg/day providing 90% efficacy. Pregabalin was safe and well tolerated across the entire dosing range.

The four diagnostic criteria for Restless Legs Syndrome are unable to exclude confounding conditions ("mimics")

BACKGROUND

Epidemiological survey studies have suggested that a large fraction of the adult population, from five to more than 10%, have symptoms of Restless Legs Syndrome (RLS). Recently, however, it has become clear that the positive predictive value of many questionnaire screens for RLS may be fairly low and that many individuals who are identified by these screens have other conditions that can "mimic" the features of RLS by satisfying the four diagnostic criteria. We noted the presence of such confounders in a case-control family study and sought to develop methods to differentiate them from true RLS.

METHODS

Family members from the case-control study were interviewed blindly by an RLS expert using the validated Hopkins telephone diagnostic interview (HTDI). Besides questions on the four key diagnostic features of RLS, the HTDI contains open-ended questions on symptom quality and relief strategies and other questions to probe the character of provocative situations and modes of relief. Based on the entire HDTI, a diagnosis of definite, probable or possible RLS or Not-RLS was made.

RESULTS

Out of 1255 family members contacted, we diagnosed 1232: 402 (32.0%) had definite or probable RLS, 42 (3.3%) possible RLS, and 788 (62.8%) Not-RLS. Of the 788 family members who were determined not to have RLS, 126 could satisfy all four diagnostic criteria (16%). This finding indicates that the specificity of the four criteria was only 84%. Those with mimic conditions were found to have atypical presentations whose features could be used to assist in final diagnosis.

CONCLUSION

A variety of conditions, including cramps, positional discomfort, and local leg pathology can satisfy all four diagnostic criteria for RLS and thereby "mimic" RLS by satisfying the four diagnostic criteria. Definitive diagnosis of RLS, therefore, requires exclusion of these other conditions, which may be more common in the population than true RLS. Short of an extended clinical interview and workup, certain features of presentation help differentiate mimics from true RLS.

Cost-effectiveness of licensed treatment options for restless legs syndrome in the UK and Sweden

OBJECTIVE

To estimate the cost-effectiveness of pramipexole versus no treatment and ropinirole in moderate to very severe idiopathic restless legs syndrome (RLS) in the UK and Sweden.

METHODS

A Markov model was developed using clinical trial data for pramipexole and ropinirole. Model health states were based on the International RLS Study Group Rating Scale (IRLS) scores. Health states were: no (IRLS 0), mild (IRLS 1-14), moderate (IRLS 15-24), severe (IRLS 25-34), very severe RLS (IRLS 35-40) and death. Patients entered the model with an IRLS score > 15 matching the trial inclusion criteria of the pramipexole trials. Resource use and utilities were based on trial data, literature, a patient survey and a panel of physicians from the UK and Sweden in the absence of published information. A healthcare sector perspective was taken for the UK and a societal perspective for Sweden using 2004-2005 unit costs. The base case analysis took a 1-year timeframe.

RESULTS

In the UK the incremental cost per quality-adjusted life year (QALY) for pramipexole was 3349 pounds sterling versus no treatment and a cost-saving of 92 pounds sterling against ropinirole. In Sweden, pramipexole produced cost-savings of Swedish Krona (SEK) 2381 (176 pounds sterling) versus no treatment and SEK 3564 (264 pounds sterling) against ropinirole. QALY gains in both countries were 0.095 versus no treatment and 0.007 versus ropinirole. Results compare well with UK cost-effectiveness thresholds of 20,000 pounds sterling/30,000 pounds sterling per QALY and are cost-saving for Sweden. One-way and probabilistic sensitivity analyses showed results to be robust.

CONCLUSIONS

Pramipexole is cost-effective compared to no treatment and ropinirole for patients with moderate to very severe RLS.

Advanced formulation design: improving drug therapies for the management of severe and chronic pain

Chronic pain is a condition affecting a vast patient population and resulting in billions of dollars in associated health care costs annually. Sufferers from severe chronic pain often require [correction of requite] twenty-four hour drug treatment through intrusive means and/or repeated oral dosing. Although the oral route of administration is most preferred, conventional immediate release oral dosage forms lead to inconvenient and suboptimal drug therapies for the treatment of chronic pain. Effective drug therapies for the management of chronic pain therefore require advanced formulation design to optimize the delivery of potent analgesic agents. Ideally, these advanced delivery systems provide efficacious pain therapy with minimal side effects via a simple and convenient dosing regime. In this article, currently commercialized and developing drug products for pain management are reviewed with respect to dosage form design as well as clinical efficacy. The drug delivery systems reviewed herein represent advanced formulation designs that are substantially improving analgesic drug therapies.