Medications that cause tremors: the TREMORS acronym

Medications that cause tremors can produce rest tremor, action tremor, or both. When evaluating a possible drug-induced tremor, the medication class and tremor type can help narrow down the cause. Learn the TREMORS acronym to remember the main drug classes and recognize the tremor types associated with each.

In this lesson from our Tremors Masterclass course, you'll learn how to:

• Use the TREMORS acronym to remember the main medication classes that can cause tremor
• Use rest, action, and mixed tremor to help narrow down a possible drug-induced cause
• Recognize that atypical antipsychotics can still cause tremor and parkinsonism
• Recognize that therapeutic lithium levels do not rule out lithium tremor
• Distinguish antiemetics that can cause tremor from those that do not

Medications that cause tremors: the TREMORS acronym

[0:00]
Several classes of drugs can cause tremor. To make them easier to remember, we came up with the acronym TREMORS, which highlights the main ones. T stands for typical/atypical antipsychotics and antiemetics. These are our dopamine-blocking agents. R stands for reversible inhibitors of VMAT2. These are our dopamine-depleting agents. E represents antiepileptic drugs. M is for mood stabilizers and antidepressants. O stands for immunosuppressants. R is for rhythm control drugs. These are the antiarrhythmics. And lastly, S stands for CNS stimulants and sympathomimetic agents.

How dopamine-blocking drugs cause tremor

[0:46]
Let's start with T, the typical/atypical antipsychotics and antiemetics. These dopamine-blocking agents cause tremor and parkinsonism by preventing dopamine from working. They bind to dopamine receptors, but don't activate them. This prevents dopamine from binding, leading to decreased signaling. More often than not, the tremor will be a rest tremor, but a pure action tremor or mixed rest/action tremor can also result from using these medications. First-generation, or typical, antipsychotics are potent blockers of the dopamine receptor. The best-known example is haloperidol, but please refer to your handbook for a more complete list.

Can atypical antipsychotics cause tremor?

[1:32]
First-generation antipsychotics are much more likely to cause tremor and parkinsonism than the second-generation, or atypical, antipsychotics. This is because the second-generation ones have a lower affinity for the dopamine receptor. However, it's important to be aware that drug-induced tremor or parkinsonism is still possible with these second-generation antipsychotics. Examples include brexpiprazole and aripiprazole. 

Which antiemetics cause tremor?

[2:01]
Antiemetics such as prochlorperazine or metoclopramide have a structure similar to the typical antipsychotics, so they can also cause tremor. Other antiemetics, like those in the ondansetron class, block serotonin receptors rather than dopamine receptors, so they're not associated with drug-induced tremor or parkinsonism.

VMAT2 inhibitors and drug-induced tremor

[2:24]
Next, R stands for reversible inhibitors of vesicular monoamine transporter type 2, or VMAT2. These are our dopamine-depleting agents. VMAT2 is a membrane protein that moves dopamine into synaptic vesicles for storage and later release. Reversible inhibitors bind to VMAT2, preventing dopamine from being packaged in vesicles and prepared for release. These include tetrabenazine, deutetrabenazine, and valbenazine. They're commonly used to treat chorea in Huntington's disease or tardive dyskinesia. Patients typically present with a rest tremor, but they may develop an action tremor or mixed tremor.

Tremor from phenytoin and valproic acid

[3:08]
E is for antiepileptic agents causing tremor, including phenytoin and valproic acid. These are older antiepileptic medications and aren't used as much to treat seizures, but valproic acid is used as a mood-stabilizing agent. These medications tend to cause more of an action tremor, but valproic acid may also cause a rest tremor or a mixed tremor.

Lithium tremor and antidepressant-induced tremor

[3:37]
M is for mood stabilizers and antidepressants. Lithium is a common mood stabilizer causing tremor. It causes more of an action tremor or mixed tremor. While tremor is more likely with high lithium levels, they can still occur with therapeutic levels. Tremor is also a possible side effect of all selective serotonin reuptake inhibitors, or SSRIs, serotonin norepinephrine reuptake inhibitors, or SNRIs, and tricyclic antidepressants, though the tremor may be slight or mild.

Immunosuppressant-induced tremor

[4:13]
O is for immunosuppressants. For example, steroids are a common cause of tremor. Other immunosuppressants, like tacrolimus and cyclosporine, can also induce tremor. Immunosuppressants predominantly cause an action tremor, but high doses or chronic exposure may lead to a mixed tremor with resting components due to neurotoxicity.

Which antiarrhythmic drugs cause tremor?

[4:40]
Next is R, which stands for rhythm control drugs. Amiodarone is the antiarrhythmic drug that most commonly induces tremor. However, others such as mexiletine and procainamide may also cause tremor. These typically cause more of an action tremor, but a mixed tremor may be seen in severe neurotoxicity cases.

Stimulants and sympathomimetics: action tremor

[5:04]
And finally, it's important to remember that agents that stimulate the central nervous system or enhance the sympathetic nervous system may cause tremor. Common examples include caffeine, cocaine, nicotine, theophylline, some bronchodilators such as salbutamol, methylphenidate, and amphetamine salts. These typically cause an action tremor. Knowing whether these medications produce more of an action or rest tremor can help narrow down the cause of your patient's tremor. You can find this complete chart in your course handbook, so be sure to check it out as a quick reference.