Can Cardizem (Diltiazem) Cause Tremors?
Tremor is not a commonly recognized adverse effect of diltiazem based on major cardiology guidelines, though rare case reports suggest it may occur, particularly with long-term use or in combination with other medications.
Evidence from Guidelines and Drug Labels
The most comprehensive evidence comes from major cardiology society guidelines that systematically document diltiazem's adverse effect profile:
Well-Established Adverse Effects
According to multiple ACC/AHA/HRS guidelines 1, the documented adverse effects of diltiazem include:
- Cardiovascular: Hypotension, bradycardia, worsening heart failure in patients with pre-existing ventricular dysfunction, AV block, edema
- Hepatic: Abnormal liver function studies, acute hepatic injury (rare)
- Other: Headache, rash, constipation, dizziness, fatigue
Notably, tremor is conspicuously absent from these comprehensive adverse effect listings across multiple high-quality guidelines.
Comparison with Other Antiarrhythmic Agents
The 2018 AHA/ACC/HRS guideline on ventricular arrhythmias 2 provides a detailed pharmacological characteristics table that lists tremor as a common adverse effect of amiodarone (along with ataxia, peripheral neuropathy) and flecainide (along with dizziness, vision disturbance). However, diltiazem's adverse effect profile in this same table lists only: hypotension, edema, heart failure, AV block, bradycardia, headache, rash, and constipation—no mention of tremor.
Case Report Evidence
One published case report 3 describes myoclonus (not typical tremor) associated with long-term diltiazem use:
- 61-year-old man on diltiazem for 5 years developed abnormal body movements
- Symptoms improved 50% within 2 weeks of discontinuation but persisted for years
- Concomitant citalopram use may have contributed
- Classified as "possible" diltiazem-induced myoclonus using the Naranjo algorithm
This represents an extremely rare occurrence with atypical features (delayed onset after years, prolonged persistence after discontinuation).
Clinical Context and Differential Diagnosis
If a patient on diltiazem develops tremor, consider:
Other medications: Beta-blockers (which are often co-administered with diltiazem) do not typically cause tremor either based on guideline documentation 1
Drug interactions: Diltiazem is a CYP3A4 inhibitor 1, 4, which could increase levels of other medications that DO cause tremor
Alternative diagnoses: Essential tremor, Parkinson's disease, metabolic disturbances, thyroid dysfunction, or other neurological conditions
Concomitant medications: Review for drugs known to cause tremor (lithium, valproate, SSRIs, stimulants, corticosteroids)
Practical Recommendation
If tremor develops in a patient taking diltiazem, it is more likely coincidental or related to other factors rather than directly caused by diltiazem. However, given the rare case report of movement disorders with long-term use 3:
- Conduct a thorough medication review for other tremor-inducing agents
- Evaluate for neurological and metabolic causes
- If no alternative explanation is found and tremor is significantly impairing quality of life, consider switching to an alternative rate-control agent (such as a beta-blocker if not contraindicated)
- Document the temporal relationship between diltiazem initiation/dose changes and tremor onset
The absence of tremor from comprehensive guideline adverse effect profiles 1, 2, 1 and FDA labeling 4 suggests this is not a recognized class effect or common adverse reaction requiring routine monitoring.