What is the relationship between Carbamazepine (anticonvulsant) and muscle jerks, also known as myoclonus?

From the Guidelines

Carbamazepine is a highly effective treatment for muscle jerks, particularly those associated with paroxysmal kinesigenic dyskinesia, with over 85% of patients achieving complete remission with low-dose therapy 1. The medication works by stabilizing nerve membranes and reducing excessive electrical activity in the brain. For muscle jerks, the initial dosage of carbamazepine is recommended to be 50 mg and can be adjusted according to the practical effect 1. Some key points to consider when using carbamazepine for muscle jerks include:

• The dosage should be flexible, as the extent of satisfaction with the treatment is subjective and individualized 1
• Common side effects include dizziness, drowsiness, nausea, and potential blood count abnormalities 1
• Regular blood monitoring is necessary, especially during the first few months of treatment, to minimize the risk of adverse effects such as Steven-Johnson syndrome/toxic epidermal necrolysis, particularly in the Han Chinese population 1
• HLA-B*15:02 screening should be implemented before initiating treatment to reduce the risk of adverse cutaneous reactions 1
• The medication should be taken at bedtime to minimize the adverse effect of dizziness 1
• Improvement in muscle jerks may take several days to weeks, and if you experience rash, severe dizziness, vision changes, or unusual bleeding, seek immediate medical attention 1. It's also important to note that carbamazepine may interact with many medications, so it's crucial to inform your doctor about all drugs you're taking 1. In cases where patients cannot tolerate carbamazepine, other voltage-gated sodium channel blockers, including lamotrigine, topiramate, and phenytoin sodium, are recommended as second-line treatment 1. Overall, carbamazepine is a valuable treatment option for muscle jerks, and its use should be guided by the most recent and highest-quality evidence, such as the expert consensus in China 1.

From the FDA Drug Label

Musculoskeletal System:Aching joints and muscles, and leg cramps. The answer is that carbamazepine may cause muscle jerks or related symptoms such as leg cramps and aching joints and muscles 2.

From the Research

Carbemazepine and Muscle Jerks

• Carbamazepine is a medication used to treat epilepsy and other neurological disorders, but it can have adverse effects, including muscle jerks 3, 4.
• A study published in 2000 found that carbamazepine can aggravate juvenile myoclonic epilepsy, leading to increased myoclonic jerks in 57.5% of patients 3.
• Another study published in 2020 reviewed the literature on carbamazepine-associated movement disorders, including myoclonus, dystonia, and dyskinesia, and found that the mean time to onset of these disorders was 33.59 days 4.
• The same study found that the most common form of management for carbamazepine-associated movement disorders was drug withdrawal, and that the mean recovery period was 8.7 days 4.
• A study published in 1997 found that increasing doses of carbamazepine can cause side effects such as dizziness, ataxia, and drowsiness, which can improve after the dose has reached a stable level 5.
• The study also found that posturography and neuropsychological tests can be used to objectively measure the effects of carbamazepine on postural stability and cognitive function 5.

Mechanisms and Management

• The mechanisms underlying carbamazepine-associated movement disorders are not fully understood, but it is thought that the metabolite CBZ-10,11-epoxide may play a role 6.
• Pharmacogenetic studies may help to identify biomarkers for carbamazepine-induced adverse reactions, including movement disorders 6.
• Management of carbamazepine-associated movement disorders typically involves drug withdrawal, but other treatments such as dose reduction or switching to a different medication may also be effective 4.

Clinical Implications

• Clinicians should be aware of the potential for carbamazepine to cause muscle jerks and other movement disorders, particularly in patients with a history of epilepsy or other neurological disorders 3, 4.
• Patients taking carbamazepine should be monitored closely for signs of adverse reactions, including muscle jerks, dizziness, and drowsiness 5.
• Further research is needed to fully understand the mechanisms underlying carbamazepine-associated movement disorders and to develop effective treatments for these conditions 6, 4.