Phase 1A safety assessment of intravenous amitriptyline

p.L1612P, a Novel Voltage-gated Sodium Channel Nav1.7 Mutation Inducing a Cold Sensitive Paroxysmal Extreme Pain Disorder

Background:

Mutations in the SCN9A gene cause chronic pain and pain insensitivity syndromes. We aimed to study clinical, genetic, and electrophysiological features of paroxysmal extreme pain disorder (PEPD) caused by a novel SCN9A mutation.

Methods:

Description of a 4-generation family suffering from PEPD with clinical, genetic and electrophysiological studies including patch clamp experiments assessing response to drug and temperature.

Results:

The family was clinically comparable to those reported previously with the exception of a favorable effect of cold exposure and a lack of drug efficacy including with carbamazepine, a proposed treatment for PEPD. A novel p.L1612P mutation in the Nav1.7 voltage-gated sodium channel was found in the four affected family members tested. Electrophysiologically the mutation substantially depolarized the steady–state inactivation curve (V1/2 from −61.8 ± 4.5 mV to −30.9 ± 2.2 mV, n = 4 and 7, P < 0.001), significantly increased ramp current (from 1.8% to 3.4%, n = 10 and 12) and shortened recovery from inactivation (from 7.2 ± 5.6 ms to 2.2 ± 1.5 ms, n = 11 and 10). However, there was no persistent current. Cold exposure reduced peak current and prolonged recovery from inactivation in wild-type and mutated channels. Amitriptyline only slightly corrected the steady–state inactivation shift of the mutated channel, which is consistent with the lack of clinical benefit.

Conclusions:

The novel p.L1612P Nav1.7 mutation expands the PEPD spectrum with a unique combination of clinical symptoms and electrophysiological properties. Symptoms are partially responsive to temperature but not to drug therapy. In vitro trials of sodium channel blockers or temperature dependence might help predict treatment efficacy in PEPD.

Information for physicians and pharmacists about drugs that might cause dry mouth: a study of monographs and published literature

BACKGROUND

Over three-quarters of the older population take medications that can potentially cause dry mouth. Physicians or pharmacists rarely inform patients about this adverse effect and its potentially severe damage to the teeth, mouth and general health.

OBJECTIVES

The objectives of this study were to (1) identify warnings in the literature about dry mouth associated with the most frequently prescribed pharmaceutical products in Canada; and (2) consider how this information might be obtained by physicians, pharmacists and patients.

METHODS

Monographs on the 72 most frequently prescribed medications during 2010 were retrieved from the Compendium of Pharmaceuticals and Specialties (CPS, a standard drug information reference for physicians and pharmacists), the National Library of Medicine's 'DailyMed' database, directly from the manufacturers, and from a systematic search of biomedical journals.

RESULTS

The CPS provided monographs for 43% of the medications, and requests to manufacturers produced the remaining monographs. Mentions of dry mouth were identified in 61% of the products (43% amongst CPS monographs; an additional 43% amongst manufacturers' monographs; 7% in the DailyMed database and 7% from biomedical journals); five medications had contradictory reports in different monographs.

CONCLUSION

Nearly two-thirds (61%) of the most commonly prescribed medications can cause dry mouth, yet warnings about this adverse effect and its potentially serious consequences are not readily available to physicians, pharmacists, dentists or patients.

Intravenous lidocaine in the treatment of refractory headache: a retrospective case series

BACKGROUND

New treatments are needed to treat chronic daily headache (CDH) and chronic cluster headache (CCH). New treatments are needed to treat this population and intravenous (IV) lidocaine is a novel treatment for CDH.

OBJECTIVE

The aim of this study was to examine the use of IV lidocaine for refractory CDH patients in an inpatient setting.

METHODS

This was an open-label, retrospective, uncontrolled study of IV lidocaine for 68 intractable headache patients in an inpatient setting. We reviewed the medical records of patients receiving IV lidocaine between February 6, 2003 and June 29, 2005.

RESULTS

Pretreatment headache scores averaged 7.9 on an 11-point scale and posttreatment scores averaged 3.9 representing an average change of 4. Average length of treatment was 8.5 days. Lidocaine infusion was generally well tolerated with a low incidence of adverse events leading to discontinuation of treatment.

CONCLUSIONS

This study suggests benefit of lidocaine treatment and the need for further prospective analyses. The mechanism of lidocaine in treating headache is unknown.

Postthoracotomy pain management problems

Pain after thoracotomy is very severe, probably the most severe pain experienced after surgery. Thoracic epidural analgesia has greatly improved the pain experience and its consequences and has been considered the standard for pain management after thoracotomy. This view has been challenged recently by the use of paravertebral nerve blocks. Nevertheless, severe ipsilateral shoulder pain and the prevention of the postthoracotomy pain syndrome remain the most important challenges for management of postthoracotomy pain.