What is a Drug-Induced Tremor?
A drug-induced tremor is an involuntary, rhythmic shaking of a part of the body caused by a medication [1.6.1]. These tremors are typically a nervous system and muscle response to certain drugs [1.2.1]. The majority of medication-induced tremors are classified as postural or action tremors [1.5.2]. This means the shaking appears when you try to hold a body part against gravity, like holding your hands outstretched, or when you perform a voluntary movement, such as writing or drinking from a cup [1.5.2, 1.6.5]. This is distinct from the resting tremor often associated with Parkinson's disease, which occurs when muscles are relaxed [1.5.5]. The shaking is usually fast, with about 4 to 12 movements per second, and often affects both sides of the body equally [1.6.5, 1.5.2].
How and Why Do Medications Cause Tremors?
The exact mechanisms behind why many medications cause tremors are not fully known, but they often involve interference with complex neurological pathways [1.4.1]. Many medication-induced tremors are considered an "enhanced physiological tremor" (EPT), where a drug amplifies the natural, usually invisible, tremor that everyone has [1.4.7]. This can happen through several pathways:
- Dopamine Blockade: Some drugs, particularly antipsychotics and certain anti-nausea medications, block dopamine receptors in the brain [1.4.4, 1.7.5]. This disruption of the brain's nigrostriatal pathway can lead to parkinsonism, a collection of symptoms including a resting tremor that mimics Parkinson's disease [1.4.4].
- Serotonergic and Noradrenergic Effects: Antidepressants like SSRIs and tricyclic antidepressants (TCAs) alter levels of neurotransmitters such as serotonin and norepinephrine [1.2.4, 1.7.5]. Overstimulation of certain serotonin receptors or increased noradrenergic activity is thought to contribute to tremors [1.4.7, 1.4.2].
- Peripheral Muscle Activation: Some medications, like beta-agonist asthma inhalers (e.g., albuterol), can act directly on beta-2-adrenergic receptors located on muscle fibers [1.7.5, 1.4.7]. This stimulation can lead to increased muscle activity and shaking [1.7.5].
- Other Mechanisms: Other drugs can induce tremors through unique pathways. For example, the heart medication amiodarone can affect both the nervous system and thyroid hormone levels, while the mood stabilizer lithium can also lead to an EPT [1.7.5, 1.4.7].
Common Classes of Medications That Trigger Tremors
A wide array of medications can induce tremors. It's a known side effect across many different drug categories [1.2.1, 1.7.1].
Psychiatric and Neurological Medications
This is one of the most common groups of tremor-inducing drugs.
- Antidepressants: Selective serotonin reuptake inhibitors (SSRIs) like fluoxetine (Prozac), tricyclic antidepressants (TCAs) like amitriptyline, and others like bupropion (Wellbutrin) are frequent culprits [1.2.1, 1.7.4].
- Mood Stabilizers: Lithium is well-known for causing a fine, high-frequency tremor in a large percentage of patients [1.3.3, 1.7.4].
- Antipsychotics: Both typical (e.g., haloperidol) and atypical (e.g., risperidone) antipsychotics can cause tremors by blocking dopamine receptors [1.2.4, 1.7.6].
- Seizure Medications: Drugs like divalproex sodium (Depakote) and valproic acid are known to cause tremors [1.2.1, 1.7.4].
Cardiovascular and Respiratory Drugs
- Asthma Medications: Beta-agonist bronchodilators such as albuterol and salmeterol are a very common cause, with some studies suggesting 7% to 20% of users experience shaking [1.2.1, 1.2.4].
- Heart Medications: The antiarrhythmic drug amiodarone can induce a postural and action tremor [1.2.1, 1.4.2]. Certain blood pressure medicines can also be a cause [1.2.1].
Other Common Culprits
- Immunosuppressants: Medications like cyclosporine and tacrolimus, used to prevent organ transplant rejection, often cause tremors [1.2.1, 1.7.4].
- Stimulants: Substances like caffeine and amphetamines are well-known for causing or worsening tremors [1.2.1].
- Antibiotics: Though less common, certain antibiotics have been linked to tremors, including fluoroquinolones (ciprofloxacin) and macrolides (erythromycin) [1.2.1, 1.7.7].
- Hormones: Taking too much thyroid medicine, such as levothyroxine, can lead to tremors similar to those seen in hyperthyroidism [1.7.1, 1.7.4].
Comparison: Drug-Induced vs. Other Common Tremors
Distinguishing between tremor types is crucial for accurate diagnosis. While a doctor's evaluation is essential, some key differences exist [1.5.2].
| Feature | Drug-Induced Tremor | Parkinson's Disease Tremor | Essential Tremor |
|---|---|---|---|
| When it Occurs | Primarily with action or holding a posture (e.g., arms outstretched) [1.5.2, 1.5.5]. | Primarily at rest; often lessens during movement [1.5.5]. | Primarily with action and posture; can be mild at rest [1.5.5]. |
| Symmetry | Typically affects both sides of the body symmetrically [1.5.2]. | Usually starts asymmetrically, affecting one side more than the other [1.5.2]. | Usually bilateral (both sides) [1.5.5]. |
| Associated Symptoms | Generally limited to tremor; other neurological signs are rare [1.5.2]. | Often accompanied by rigidity, slowness of movement (bradykinesia), and balance problems [1.6.3]. | Typically no other neurological symptoms [1.6.6]. |
| Handwriting | Can be large and shaky. | Often becomes very small (micrographia) [1.5.6]. | Often large and tremulous [1.5.6]. |
| Response to stopping drug | Tremor usually resolves, though it can take weeks to months [1.6.1, 1.6.3]. | Unrelated to medication initiation/cessation. | Unrelated to medication initiation/cessation. |
Diagnosis and Management
Diagnosing a drug-induced tremor begins with a thorough review of your medication history [1.6.1]. The timing of the tremor's onset in relation to starting a new medication is a key clue [1.5.2]. The primary treatment strategy is to identify and address the offending medication [1.6.1]. Never stop or change the dose of a prescribed medication without consulting your healthcare provider [1.6.1, 1.5.2].
Management strategies include:
- Discontinuation: If possible, the provider may stop the suspected medication. The tremor often resolves, though it can sometimes take several months [1.6.3].
- Dose Reduction: Lowering the dose of the medication can sometimes reduce or eliminate the tremor while maintaining the therapeutic benefit of the drug [1.6.4].
- Switching Medications: The provider might switch to an alternative drug in the same class that is less likely to cause tremors [1.6.4].
- Adding a Medication: In cases where the offending drug is essential and cannot be changed, another medication like a beta-blocker (e.g., propranolol) may be prescribed to help control the tremor [1.6.1, 1.2.4].
- Lifestyle Adjustments: Avoiding stimulants like caffeine can help, as they can worsen tremors [1.6.1].
Conclusion
Drug-induced tremor is a common and treatable side effect of many widely used medications. It is typically a postural or action tremor affecting both sides of the body. The underlying cause often relates to the medication's effect on neurotransmitters like dopamine and serotonin or direct effects on muscle tissue. Diagnosis relies heavily on a careful medication history. Management focuses on stopping, reducing, or switching the causative drug, always under the guidance of a healthcare professional. While bothersome, these tremors are not usually dangerous and often resolve once the medication is adjusted.
For more information, you can visit the National Institute of Neurological Disorders and Stroke (NINDS).
