Understanding Myoclonus: What Drugs Cause Jerking?

October 10, 2025 •

3 min read

According to a French pharmacovigilance database study, drug-induced myoclonus accounted for 0.2% of all adverse drug reaction reports [1.3.2]. Understanding what drugs cause jerking is crucial for patients and healthcare providers to recognize and manage this potential side effect, known as myoclonus.

Quick Summary

A wide array of medications can induce myoclonus, which are sudden, involuntary muscle jerks. This overview details the primary drug classes responsible, including opioids, antidepressants, and antibiotics, and explains how to manage this condition.

Key Points

Diverse Causes: Many drug classes, including antidepressants, opioids, antipsychotics, and antibiotics, are known to cause involuntary muscle jerking (myoclonus) [1.2.1].
Neurotransmitter Impact: These drugs typically induce myoclonus by altering the activity of neurotransmitters like serotonin, dopamine, and GABA in the central nervous system [1.2.4].
Antidepressant Link: All classes of antidepressants (SSRIs, TCAs, SNRIs) can cause myoclonus due to their influence on serotonin pathways [1.6.1, 1.2.2].
Opioid Risk: High doses or chronic use of opioids like morphine and fentanyl are strongly associated with myoclonic jerks [1.7.2, 1.7.4].
Primary Treatment: The most effective management for drug-induced myoclonus is the careful withdrawal or dose reduction of the offending medication, under medical supervision [1.5.2].
Symptomatic Relief: If the causative drug cannot be stopped, medications like clonazepam or levetiracetam may be used to help reduce symptoms [1.5.6].
Paradoxical Effect: Some anticonvulsant drugs, normally used to control seizures, can paradoxically cause or worsen myoclonus in certain situations [1.2.6].

What is Myoclonus?

Myoclonus is characterized by sudden, brief, shock-like involuntary movements caused by muscle contractions or relaxations [1.7.4]. These jerks can vary in intensity and frequency, ranging from minor, barely noticeable twitches to severe, repeated spasms that interfere with normal activities like eating, speaking, or walking [1.5.6]. While myoclonus can be a symptom of various neurological disorders, including epilepsy, it can also be a side effect of numerous medications. This is known as drug-induced myoclonus [1.2.4].

The Link Between Medications and Muscle Jerking

Many different types of drugs can cause myoclonus by affecting the central nervous system, particularly neurotransmitter systems involving serotonin, dopamine, GABA, and glutamate [1.2.4]. The presentation of drug-induced myoclonus can be diverse, affecting a single muscle (focal), a group of muscles, or the entire body (generalized) [1.2.4]. The most frequently reported classes of drugs to cause this condition are opioids, antidepressants, antipsychotics, and antibiotics [1.2.1, 1.4.6].

Common Drug Classes That Cause Jerking

A vast range of medications has been associated with myoclonus. It is a critical adverse effect to recognize, as it is often reversible upon discontinuation of the offending drug [1.5.2].

Antidepressants: All classes of antidepressants, including tricyclic antidepressants (TCAs), selective serotonin reuptake inhibitors (SSRIs), and serotonin-norepinephrine reuptake inhibitors (SNRIs), have been reported to cause myoclonus at both therapeutic and toxic doses [1.6.1]. This is often linked to their impact on the brain's serotonin levels [1.2.2, 1.6.4]. Myoclonus from antidepressants can be multifocal or generalized and may even present as stuttering speech with jaw myoclonus [1.6.1]. One study noted that while 30% of patients on cyclic antidepressants experienced some myoclonus, it was only clinically significant in 9% of them [1.3.3].

Opioids: The use of opioids like morphine, fentanyl, hydromorphone, and tramadol is a well-documented cause of myoclonus, particularly at high doses or during chronic administration [1.2.3, 1.7.2]. The incidence of opioid-related myoclonus varies widely in studies, from 2.7% to 87% [1.7.1]. It is thought to be a neuroexcitatory effect, possibly caused by the accumulation of certain metabolites [1.7.2, 1.7.4]. The movements are often multifocal and stimulus-sensitive.

Antipsychotics: Both first-generation (e.g., haloperidol) and second-generation (e.g., clozapine, risperidone) antipsychotics can induce myoclonus [1.2.2, 1.4.1, 1.6.4]. These drugs primarily affect dopamine receptors, which can disrupt the brain's control over muscles, leading to jerky movements [1.2.2, 1.4.5].

Antibiotics: Several classes of antibiotics are associated with myoclonus, including penicillins, cephalosporins, carbapenems, and fluoroquinolones [1.2.3, 1.8.2]. The neurological side effects of antibiotics are not common, with an estimated incidence of less than 1% [1.8.2]. Quinolone antibiotics in particular can cause potentially permanent side effects involving muscles and the nervous system [1.8.4].

Anticonvulsants: Paradoxically, some drugs used to treat seizures (antiepileptics) can cause or worsen myoclonus [1.2.6]. Medications such as gabapentin, pregabalin, lamotrigine, phenytoin, and valproic acid have been linked to myoclonic jerks [1.2.3]. This is particularly noted in patients with renal insufficiency or when certain combinations of these drugs are used [1.3.7].

Comparison of Drug Classes Causing Myoclonus


Drug Class	Common Examples	Typical Myoclonus Presentation
Antidepressants	Fluoxetine (SSRI), Amitriptyline (TCA), Venlafaxine (SNRI) [1.2.2, 1.6.1]	Multifocal or generalized, often action-induced; can affect jaw [1.6.1].
Opioids	Morphine, Fentanyl, Tramadol, Hydromorphone [1.2.3]	Multifocal, stimulus-sensitive jerks, especially with high doses [1.7.1, 1.7.4].
Antipsychotics	Haloperidol, Clozapine, Risperidone [1.2.2, 1.4.1]	Multifocal movements in limbs and face [1.6.4].
Antibiotics	Penicillins, Ciprofloxacin (Fluoroquinolone) [1.2.3]	Can be focal, multifocal, or propriospinal (truncal) [1.2.4, 1.2.6].
Anticonvulsants	Gabapentin, Pregabalin, Lamotrigine [1.2.3, 1.3.7]	Can worsen existing myoclonus or induce it, especially with renal issues [1.2.6, 1.3.7].

Diagnosis and Management

The first step in managing drug-induced myoclonus is identifying the causative agent [1.5.2]. A thorough review of the patient's medication history is essential. In most cases, the myoclonus resolves after withdrawing the offending drug [1.5.2]. Therefore, consulting a healthcare provider is crucial before making any changes to a medication regimen.

If the medication cannot be stopped, a dose reduction may alleviate the symptoms [1.5.2]. In cases where the myoclonus persists or is severe, other treatments may be considered. Medications like clonazepam (a tranquilizer) and certain anticonvulsants such as levetiracetam and valproic acid are commonly used to manage the symptoms, though they are not specifically designed for myoclonus [1.5.3, 1.5.6].

Conclusion

Drug-induced jerking, or myoclonus, is a recognized side effect of a wide variety of medications, from common antidepressants and painkillers to antibiotics and anticonvulsants. While often benign, it can be distressing and sometimes debilitating. Recognizing the link between a new medication and the onset of muscle jerks is the most important step toward resolution. Patients experiencing these symptoms should always consult their healthcare provider to determine the cause and find the best management strategy, which typically involves adjusting or changing the medication. Never stop a prescribed medication without medical advice. For more detailed information, one authoritative resource is the National Institute of Neurological Disorders and Stroke page on Myoclonus.

https://www.ninds.nih.gov/health-information/disorders/myoclonus

Frequently Asked Questions

The first signs are often sudden, brief, shock-like muscle twitches or jerks that you cannot control. They can be infrequent and affect a small muscle, or become more regular and involve larger muscle groups [1.7.4].

Yes, SSRIs and other antidepressants are a common cause of myoclonus. They affect serotonin levels in the brain, which can lead to involuntary jerks, twitches, or even spasms [1.2.2, 1.6.1].

In most cases, drug-induced myoclonus is reversible and will gradually resolve after the causative drug is stopped or the dosage is reduced [1.5.2]. You should consult your doctor before making any changes.

While the jerking itself is not typically life-threatening, it can be severe enough to interfere with daily activities like walking or eating, and may increase the risk of falls or injury [1.5.6]. It's important to report it to your doctor.

Opioid painkillers such as morphine, tramadol, fentanyl, and hydromorphone are most frequently associated with causing myoclonus, especially when used in high doses over a long period [1.2.3, 1.7.1].

Diagnosis is primarily based on a clinical evaluation and a thorough review of your medication history to establish a timeline between starting a drug and the onset of symptoms. In most instances, seeing the symptoms resolve after stopping the drug confirms the diagnosis [1.5.2].

The primary treatment is to withdraw the offending drug under a doctor's supervision [1.5.2]. If that is not possible, your doctor might reduce the dose or prescribe another medication like clonazepam or levetiracetam to help control the symptoms [1.5.6].