Drug-induced tremor is an involuntary, rhythmic muscle movement that appears as shaking, most commonly affecting the hands, arms, and head. This side effect is a nervous system and muscle response to certain medications, occurring when a person tries to move or hold a position. Tremors can range from a mild quiver to a significant movement that interferes with daily tasks like writing or drinking. The shaking is typically fast, ranging from about 4 to 12 movements per second, and often disappears during sleep. Understanding which drugs trigger this response is important for managing long-term treatment plans.
Common Medications That Cause Shaking
Many medications across several classes can cause or worsen tremors, including those used for mood, heart conditions, and respiratory issues.
Psychiatric medications frequently implicated include mood stabilizers, such as lithium carbonate, which is a well-known cause of dose-related tremor. This shaking is often symmetrical and can affect a patient’s ability to tolerate the medication.
Antidepressants, particularly selective serotonin reuptake inhibitors (SSRIs) and tricyclic antidepressants (TCAs), can also induce a tremor. Examples include fluoxetine and venlafaxine, which affect the brain’s chemical messengers. Certain antipsychotic drugs, such as haloperidol, cause tremors by blocking dopamine receptors in the brain.
Bronchodilators, such as beta-agonists like albuterol, are a common cause of drug-induced shaking. These asthma medications stimulate receptors that relax airway muscles, but this stimulation can extend to the muscles in the hands and arms. Up to 20% of patients using these inhalers may experience shaking, especially when starting the medication.
Other drugs linked to tremors include:
- Anti-seizure medications (anticonvulsants), such as divalproex sodium (valproate).
- Medications for heart rhythm abnormalities, such as amiodarone.
- Immunosuppressants used after organ transplant, such as cyclosporine.
- Stimulants like amphetamines.
- Excessive thyroid hormone replacement medication.
How Drugs Affect the Nervous System to Cause Shaking
Drug-induced shaking occurs because medications interfere with the complex, balanced signaling pathways of the central and peripheral nervous systems. The most common mechanism involves the enhancement of a naturally occurring, low-amplitude vibration known as physiological tremor. Drugs that increase the activity of the sympathetic nervous system, such as stimulants and bronchodilators, heighten the body’s “fight or flight” response, thereby increasing this tremor.
Many tremors result from the disruption of neurotransmitter balance, which are the chemical messengers in the brain. Medications that block dopamine receptors, such as older antipsychotics, can cause a resting tremor that mimics Parkinson’s disease. This occurs because dopamine is essential for smooth, controlled movement.
Other drug classes, including antidepressants, affect neurotransmitters like serotonin and norepinephrine. An excess of these chemicals can over-stimulate motor pathways, leading to rhythmic muscle contractions. In the case of lithium, while the exact mechanism is not fully understood, it is believed to affect various pathways, sometimes intensifying existing tremors.
The resulting tremor is typically postural or kinetic, meaning it appears when holding a position against gravity or during voluntary movement, as opposed to a tremor that occurs while the body is completely at rest. Some medications, like valproate, may also affect cerebellar function or the balance of inhibitory neurotransmitters like Gamma-aminobutyric acid (GABA). The time of onset can vary, sometimes appearing acutely after starting the drug or increasing the dose, or developing after prolonged use.
When to Seek Medical Help and Management Options
If a new or worsening tremor interferes with daily activities like eating or writing, seek medical help. Never abruptly stop taking a prescribed medication without consulting a provider first, as sudden discontinuation can worsen the tremor or lead to dangerous withdrawal symptoms.
Medical attention is necessary to confirm the tremor is drug-induced and not a symptom of an underlying condition like Parkinson’s disease or an overactive thyroid. The primary management strategy is often adjusting the dosage of the offending drug, as the tremor is frequently dose-related.
If dose reduction is not feasible, the doctor may suggest switching to a different drug within the same class that is less likely to cause shaking. If the causative medication must be continued, a secondary medication may be prescribed to control the shaking. For example, beta-blockers like propranolol are sometimes used to counteract tremors, particularly those that enhance physiological tremor.