Gabapentin may be hazardous in myasthenia gravis

Development of prescribing indicators related to opioid-related harm in patients with chronic pain in primary care-a modified e-Delphi study

BACKGROUND

Long-term opioid use is associated with dependency, addiction, and serious adverse events. Although a framework to reduce inappropriate opioid prescribing exists, there is no consensus on prescribing indicators for preventable opioid-related problems in patients with chronic pain in primary care in the UK. This study aimed to identify opioid prescription scenarios for developing indicators for prescribing opioids to patients with chronic pain in primary care.

METHODS

Scenarios of opioid prescribing indicators were identified from a literature review, guidelines, and government reports. Twenty-one indicators were identified and presented in various opioid scenarios concerning opioid-related harm and adverse effects, drug-drug interactions, and drug-disease interactions in certain disease conditions. After receiving ethics approval, two rounds of electronic Delphi panel technique surveys were conducted with 24 expert panellists from the UK (clinicians, pharmacists, and independent prescribers) from August 2020 to February 2021. Each indicator was rated on a 1-9 scale from inappropriate to appropriate. The score's median, 30th and 70th percentiles, and disagreement index were calculated.

RESULTS

The panel unanimously agreed that 15 out of the 21 opioid prescribing scenarios were inappropriate, primarily due to their potential for causing harm to patients. This consensus was reflected in the low appropriateness scores (median ranging from 1 to 3). There were no scenarios with a high consensus that prescribing was appropriate. The indicators were considered inappropriate due to drug-disease interactions (n = 8), drug-drug interactions (n = 2), adverse effects (n = 3), and prescribed dose and duration (n = 2). Examples included prescribing opioids during pregnancy, concurrently with benzodiazepines, long-term without a laxative prescription and prescribing > 120-mg morphine milligram equivalent per day or long-term duration over 3 months after surgery.

CONCLUSIONS

The high agreement on opioid prescribing indicators indicates that these potentially hazardous consequences are relevant and concerning to healthcare practitioners. Future research is needed to evaluate the feasibility and implementation of these indicators within primary care settings. This research will provide valuable insights and evidence to support opioid prescribing and deprescribing strategies. Moreover, the findings will be crucial in informing primary care practitioners and shaping quality outcome frameworks and other initiatives to enhance the safety and quality of care in primary care settings.

Percutaneous Electrical Nerve Stimulation (PENS) for Infrapatellar Saphenous Neuralgia Management in a Patient with Myasthenia gravis (MG)

Myasthenia gravis is a neuromuscular transmission disorder characterized by weakness of the cranial and skeletal muscles, however, neuropathies are extremely rare. In this case report we present a case of a 61-year-old man diagnosed Myasthenia gravis who came to our attention due to a 1 week of acute deep pain [NPRS 8/10] in the anterior and medial right knee which occurred during walking [NPRS 8/10] or stair climbing [NPRS 9/10]. A complete medical record and clinical examination based on physical exploration and ultrasound assessment confirmed a infrapatellar saphenous neuralgia. Therapeutic interventions included Percutaneous nerve electrical stimulation combined with pain neuroscience education, neural mobilization of the saphenous nerve and quadriceps resistance exercises. After 4 weeks, pain intensity [NRPS = 1/10], knee functionality [OKS = 41/48] and lower limb functionality [LLFI = 80%] were notably improved, nevertheless, fatigue [RPE = 2/10] was similar than baseline. At 2 months of follow-up, the effect on intensity of pain NRPS [0/10] and functionality OKS [40/48] and LLFI [82%] was maintained, however, no significant clinical changes were detected on perceived fatigue RPE Scale [2/10]. Despite the important methodological limitations of this study, our case report highlights the efficacy of percutaneous electrical nerve stimulation combined with physical agents modalities for pain and functionality of infrapatellar saphenous neuralgia in the context of Myasthenia gravis.

Drugs That Induce or Cause Deterioration of Myasthenia Gravis: An Update

Myasthenia gravis (MG) is an autoimmune neuromuscular disorder which is characterized by presence of antibodies against acetylcholine receptors (AChRs) or other proteins of the postsynaptic membrane resulting in damage to postsynaptic membrane, decreased number of AChRs or blocking of the receptors by autoantibodies. A number of drugs such as immune checkpoint inhibitors, penicillamine, tyrosine kinase inhibitors and interferons may induce de novo MG by altering the immune homeostasis mechanisms which prevent emergence of autoimmune diseases such as MG. Other drugs, especially certain antibiotics, antiarrhythmics, anesthetics and neuromuscular blockers, have deleterious effects on neuromuscular transmission, resulting in increased weakness in MG or MG-like symptoms in patients who do not have MG, with the latter usually being under medical circumstances such as kidney failure. This review summarizes the drugs which can cause de novo MG, MG exacerbation or MG-like symptoms in nonmyasthenic patients.

Worsening of myasthenia due to antiepileptic, antipsychotic, antidepressant, and sedative medication: An estimation of risk based on reporting frequency

BACKGROUND AND PURPOSE

Many drugs can worsen myasthenia symptoms. The clinician usually relies on cautionary lists compiled according to case reports. We intended to provide a quantitative basis for a risk comparison within the groups of antiepileptic, antidepressant, neuroleptic, and sedative drugs.

METHODS

We extracted adverse drug reaction (ADR) counts (total and myasthenia related) for drugs from these groups and calculated the reporting odds ratio (ROR) within the drug groups from the World Health Organization pharmacovigilance database. For a given drug, the ROR was increased above 1 if the proportion of myasthenia-related ADRs for this drug was larger than the same proportion for the rest of drugs in that same group. If the 95% confidence interval of ROR was >1, this was taken as a signal for a higher risk of the given drug as compared to the average of the respective group.

RESULTS

Gabapentin, sertraline, citalopram, lithium, and amisulpride had a signal for the ROR to be increased above 1 within their respective groups. Bupropion, desvenlafaxine, duloxetine, escitalopram, and paroxetine had ROR values <1. For all other drugs, 1 was within the ROR confidence interval.

CONCLUSIONS

For gabapentin and lithium, the analysis of RORs confirmed case reports and cautionary lists. For a number of antidepressant drugs associated with a higher-than-average risk, no case reports exist substantiating our results. For these drugs, special attention should be paid to this risk. The remarkable difference between citalopram and escitalopram could prompt experimental work to confirm differential influence of the two preparations on neuromuscular transmission.

Herpes Zoster and Postherpetic Neuralgia in an Elderly Patient with Critical COVID-19: A Case Report

Critical patients with COVID-19 are thought to be at high risk of developing chronic pain. However, the exact nature and mechanisms of COVID-19-related chronic pain remain largely unknown. Here, we describe clinical features, treatments and outcome of herpes zoster as well as postherpetic neuralgia in a 70-year-old woman with critical COVID-19. The patient had a history of type 2 diabetes and myasthenia gravis. She developed herpes zoster in the right 10 to 12 lumbar dermatomes in the recovery period of COVID-19. Intravenous (250 mg 3 times a day) and then oral (400 mg 5 times a day) acyclovir was used for antiviral therapy. Pregabalin (75 mg orally twice a day) and ibuprofen was used for analgesia. Her skin lesions resolved 21 days after the onset of rash. However, she continued to have persistent pain in the same dermatomal distribution. After the dosage of pregabalin was increased to 150 mg orally twice a day, her pain was partially relieved. During the telephone follow-up 4 months after herpes zoster eruption, the patient still complained intermittent pain in the right 10 to 12 lumbar dermatomes. Our case draws attention to postherpetic neuralgia in COVID-19 patients and provides a targeted suggestion for this kind of patients.

An investigation on the effects of carbamazepine and sodium valproate on neuromuscular transmission

The aim of this study was to investigate the effects of sodium valproate (SV) and carbamazepine (CBZ) on neuromuscular transmission using single-fibre electromyography (SFEMG) in patients with epilepsy. We performed SFEMG during the voluntary contraction of extensor digitorum communis muscle. 30 epileptic patients taking SV, 25 epileptic patients taking CBZ, and 25 age-matched healthy volunteers were included in the study. Mean jitter values (MCD) of subjects taking SV and CBZ were compared with normal controls. MCD values of subjects taking SV and CBZ were statistically significantly higher than those of control group. Review of the correlation between disease duration and MCD values of patients showed that MCD values were increased with the prolonged use of drugs, and thus, indicated a positive relationship between these two parameters. These results suggest that both SV and CBZ reduce neuromuscular transmission in patients without a neuromuscular junction disease.

Management of Insomnia and Anxiety in Myasthenia Gravis

Myasthenia gravis is a neuroimmunological disorder leading to skeletal muscle weakness. Common symptoms of the disease, such as anxiety, depression, and insomnia, can cause significant distress in patients. Unfortunately, selecting an appropriate medication for treatment of psychiatric comorbidities can prove to be challenging for providers given the unique pharmacologic constraints that myasthenia gravis presents. The authors present the following clinical vignette and accompanying discussion in an attempt to highlight the special considerations that must be taken into account when treating anxiety and insomnia in patients with myasthenia gravis, as well as to provide an overview of available medication options through the lens of existing constraints.

Uncontrolled recurrent myasthenia gravis exacerbations secondary to chronic gabapentin use

Gabapentin is an anticonvulsant medication that reduces synaptic transmission by decreasing presynaptic voltage-gated Ca2+ and Na+ channels. It is approved to treat focal seizures but also used to treat post-herpetic and neuropathic pain. Although uncommon, there have been three reported cases of myasthenia gravis exacerbation associated with gabapentin in the literature. We present a patient with uncontrolled recurrent myasthenia gravis exacerbations secondary to chronic gabapentin use and provide a review for the three published cases.

Treatment of Generalized Anxiety Disorder with Gabapentin

Gabapentin is frequently used in the treatment of anxiety disorders. However, there are no randomized controlled trials on the effectiveness of this medication in generalized anxiety disorder (GAD), and there are only a few case reports. We present a case of a 59-year-old female with a psychiatric history of GAD. The patient discontinued benzodiazepines after more than 7 years of daily treatment which led to rebound anxiety, benzodiazepine withdrawal symptoms, and suicidal ideation. She was psychiatrically hospitalized and started on gabapentin. Over the next 10 months of outpatient follow-up, she attempted to taper off gabapentin due to personal preference to limit medications. During this time, we observed a clear dose-response pattern of gabapentin on GAD symptoms. In the absence of controlled studies, these findings may offer important information about the effectiveness of gabapentin in GAD.

Review about gabapentin misuse, interactions, contraindications and side effects

The current work is targeted to review the risks of gabapentin misuse, its potential interactions with other drugs, side effects and use contraindications. This review consists of a total of 99 biographical references (from the year 1983 to 2016). A publication search of PubMed was performed from January 1983 to December 2016. It included animal studies, clinical studies, case studies and reviews related to gabapentin misuse, potential interactions, side effects and use contraindications. The search terms were gabapentin, anticonvulsant and antiepileptic. In general, it seems that gabapentin has risks of being misused based on the increased level of prescriptions, related fatalities, recreational misuse and higher doses of self-administration. The main reasons for gabapentin misuse are as follows: getting high, alleviating opioid withdrawal symptoms and potentiating methadone effects. Some of the main substances that interact with gabapentin are morphine, caffeine, losartan, ethacrynic acid, phenytoin, mefloquine and magnesium oxide. Some of the side effects caused by gabapentin are teratogenicity, hypoventilation, respiratory failure and myopathy. Finally, reports in general contraindicate the use of gabapentin in conditions such as myasthenia gravis and myoclonus.

Worsening of Myasthenia Gravis following the Addition of Gabapentin for Essential Tremor

Objective:

To report a case of worsening myasthenia gravis after the initiation of gabapentin for treatment of essential tremor.

Case Summary:

A 69-year-old man experienced minor ptosis of the left eyelid, slight neck weakness, and transient difficulties in chewing food on day 6 of a slow gabapentin dosage titration. As the titration continued, the myasthenia symptoms progressed to bilateral ptosis, and there was dramatic worsening of weakness by day 23. He was taking gabapentin 1500 mg daily at the time; the drug was then tapered to discontinuation. All myasthenia gravis symptoms were reported as resolved 3 days after discontinuation of gabapentin. The initiation and discontinuation of gabapentin also coincided with improvement, then worsening of the patient's tremor.

Discussion:

Three published case reports describe worsening of myasthenia gravis during use of gabapentin for the treatment of various neuropathies. To the best of our knowledge, this is the first case report of a patient experiencing worsening of myasthenia gravis upon initiation of gabapentin for essential tremor. The Naranjo probability scale suggests a probable association between gabapentin and worsening of myasthenia gravis symptoms in our patient. Several myasthenia-like symptoms are listed in the gabapentin mongraph as low-frequency adverse events, increasing the possibility that gabapentin may have been unmasking or worsening myasthenia gravis in clinical trials. However, myasthenia gravis is not identified as a contraindication or caution for gabapentin use.

Conclusions:

Gabapentin should be used with caution in patients with myasthenia gravis, and clinicians must be aware of the potential risks of this therapy.

The long-term safety of antiepileptic drugs

Antiepileptic drugs (AEDs) are used by millions of people worldwide for the treatment of epilepsy, as well as in many other neurological and psychiatric conditions. They are frequently associated with adverse effects (AEs), which have an impact on the tolerability and success of treatment. Half the people who develop intolerable AEs discontinue treatment early on after initiation, while the majority of people will continue to be exposed to their effects for long periods of time. The long-term safety of AEDs reflects their potential for chronic, cumulative dose effects; rare, but potentially serious late idiosyncratic effects; late, dose-related effects; and delayed, teratogenic or neurodevelopmental effects. These AEs can affect every body system and are usually insidious. With the exception of delayed effects, most other late or chronic AEs are reversible. To date, there is no clear evidence of a carcinogenic effect of AEDs in humans. While physicians are aware of the long-term AEs of old AEDs (the traditional liver enzyme-inducing AEDs and valproate), information about AEs of new AEDs (such as lamotrigine, levetiracetam, oxcarbazepine, topiramate or zonisamide), particularly of their teratogenic effects, has emerged over the years. Sporadic publications have raised issues about AEs of the newer AEDs eslicarbazepine, retigabine, rufinamide, lacosamide and perampanel but their long-term safety profiles may take years to be fully appreciated. Physicians should not only be aware of the late and chronic AEs of AEDs but should systematically enquire and screen for these according to the individual AED AE profile. Care should be taken for individuals with comorbid conditions that may render them more susceptible to specific AEs. Prevention and appropriate management of long-term AED AEs is expected to improve adherence to treatment, quality of life and control of epilepsy.

The challenge of pain management in patients with myasthenia gravis

Myasthenia gravis (MG) is an autoimmune disorder of the neuromuscular junction. The complexity of the disease and its treatments make MG patients particularly susceptible to adverse effects of drugs. MG is not a painful condition; however, as pain management armamentarium includes drugs from diverse pharmacological groups and with potential for drug-drug interactions, managing pain in patients with MG can be challenging. The underlying disease and the concomitant medications of each patient must be considered and the analgesic treatment individualized. This review presents an update on the various aspects of pain pharmacotherapy in patients with MG, focusing primarily on medications used to treat chronic pain. Drugs discussed are opioids, nonsteroidal anti-inflammatory drugs, antidepressants, anticonvulsants, muscle relaxants, benzodiazepines, intravenous magnesium, and local anesthetics. Drug interactions with agents used for MG treatment (acethylcholinesterase inhibitors, corticosteroids, immunosuppressants) and plasmapheresis are discussed. The clinical usefulness and limitations of each of the drug classes and agents are described.

Gabapentin and pregabalin for chronic neuropathic and early postsurgical pain: current evidence and future directions

PURPOSE OF REVIEW

Gabapentin and pregabalin bind to the alpha-2-delta calcium channel subunit and represent a novel analgesic drug class. The evidence base supporting their use for chronic neuropathic and early postsurgical pain is reviewed.

RECENT FINDINGS

Multiple, large, high-quality trials have demonstrated the safety and efficacy of gabapentin and pregabalin in neuropathic pain. Treatment-related improvement of pain and sleep positively impact upon quality of life. Sedation, dizziness and ataxia are important and relatively common adverse effects, however. Accumulating evidence indicates that gabapentin, and possibly pregabalin, also exert important effects following surgery. Multiple high-quality trials have demonstrated analgesic and opioid-sparing efficacy with gabapentin following various surgical procedures. Gabapentin and pregabalin reduce movement-evoked pain and this can lead to enhanced functional postoperative recovery. Postoperative opioid sparing is of questionable relevance since few trials have shown reduced opioid-related adverse effects. Sedation, dizziness and ataxia have been reported in only a few trials. Future larger-scale perioperative trials focused on safety assessment are needed, however.

SUMMARY

Gabapentin and pregabalin are efficacious treatments for neuropathic and postsurgical pain. Future research addressing several specific questions would serve to better delineate their optimal roles in treating these and other pain conditions.

Stimulated-single fiber electromyography monitoring of anti-sense induced changes in experimental autoimmune myasthenia gravis

The neuromuscular weakness associated with myasthenia gravis (MG) can be transiently relieved by pharmacological inhibitors of acetylcholinesterase (AChE). Here, we expand the anticholinesterase repertoire to include 2'-O-methyl-protected antisense oligonucleotides targeted to AChE mRNA (EN101). Using stimulated-single fiber electromyography, we show that EN101 treatment of rats with experimental autoimmune myasthenia gravis (EAMG), improved the mean consecutive difference (MCD) and blocking for 24h. This treatment was more efficient than pyridostigmine and was accompanied by marked improvement in stamina and clinical profile.

Treatment of post-herpetic pain in myasthenia gravis: exacerbation of weakness due to gabapentin

Here, we present a case of a 64-year-old female suffering from a severe form of antibody-positive myasthenia gravis. Under an immunosuppressive regimen with cyclosporine A, she experienced an episode of thoracic herpes zoster followed by intense post-herpetic neuralgia. In order to avoid drug interactions as well as adverse effects of carbamazepine in myasthenia gravis, gabapentin was chosen for the treatment of neuropathic pain. Within a few days she noticed increasing weakness, but continued medication for 8 weeks as gabapentin was not identified as the hazardous agent by her physician. Acetylcholine receptor antibody levels remained unchanged, but increased decrement was observed clinically and in repetitive nerve stimulation. After withdrawal of gabapentin, she recovered quickly to her previous condition.

The role of readthrough acetylcholinesterase in the pathophysiology of myasthenia gravis

Alternative splicing induces, under abnormal cholinergic neurotransmission, overproduction of the rare "readthrough" acetylcholinesterase variant AChE-R. We explored the pathophysiological relevance of this phenomenon in patients with myasthenia gravis (MG) and rats with experimental autoimmune MG (EAMG), neuromuscular junction diseases with depleted acetylcholine receptors. In MG and EAMG, we detected serum AChE-R accumulation. In EAMG, we alleviated electromyographic abnormalities by nanomolar doses of EN101, an antisense oligonucleotide that selectively lowers AChE-R in blood and muscle yet leaves unaffected the synaptic variant AChE-S. Whereas animals treated with placebo or conventional anticholinesterases continued to deteriorate, a 4 wk daily oral administration of EN101 improved survival, neuromuscular strength and clinical status in moribund EAMG rats. The efficacy of targeting only one AChE splicing variant highlights potential advantages of mRNA-targeted therapeutics for chronic cholinergic malfunctioning.