Does Doxepin Decrease Pulse?
Doxepin does not decrease pulse; rather, it tends to increase heart rate, particularly at higher doses, and can cause tachyarrhythmias as part of its cardiovascular effects. This is consistent with its classification as a tricyclic antidepressant (TCA) with known cardiac effects 1.
Cardiovascular Effects of Doxepin
Heart Rate Effects
Doxepin's impact on heart rate is complex and dose-dependent:
At therapeutic doses: Doxepin produces a slight increase in heart rate, particularly during exertion. Studies show increases of 2-6 beats per minute, most pronounced in younger patients, attributed to the "cocaine-like effect" of tricyclic drugs 2.
In cardiac patients: Research specifically examining patients with ventricular arrhythmias found that doxepin increased heart rate rather than decreased it 3. The study showed no significant bradycardic effect at therapeutic doses.
Minimal effect at standard doses: One study in depressed patients with preexisting cardiac disease found that doxepin "did not have a robust effect on heart rate" 4, suggesting the effect is modest but tends toward increase rather than decrease.
Toxic Doses and Arrhythmias
The cardiac effects become more pronounced and dangerous at toxic levels:
Tachyarrhythmias occur first: Large intravenous doses initially cause tachyarrhythmias 5.
Bradycardia only at lethal doses: Progressive and potentially lethal bradycardia occurs only at very high toxic doses, representing end-stage cardiotoxicity 5.
Overdose manifestations: The FDA label explicitly lists "cardiac dysrhythmias" as critical manifestations of overdose, with QRS widening being a key indicator of toxicity 6.
Clinical Implications
Important Caveats
TCAs as a class increase cardiac arrest risk: Doxepin belongs to the TCA class, which has been associated with increased risk of cardiac arrest (OR 1.69) in registry studies 1. This risk is related to:
- QT interval prolongation
- AV node conduction delays leading to AV block 1
- Increased risk of sudden cardiac death, particularly in elderly patients with comorbidities
Practical Considerations
Orthostatic hypotension is the primary concern: While doxepin doesn't decrease pulse, it causes significant orthostatic hypotension, which was a major reason for discontinuation (16% dropout rate due to cardiovascular side effects) 4.
Not safer than other TCAs: Despite historical beliefs that doxepin is "safer" for the heart, evidence shows its cardiovascular effects are comparable to imipramine and nortriptyline, with no greater margin of safety 4.
Conduction effects: Doxepin slows cardiac conduction (increases PR and QRS intervals) but this is distinct from decreasing heart rate 3.
Monitoring Recommendations
For patients on doxepin, particularly those with cardiac disease:
- Monitor for tachycardia rather than bradycardia at therapeutic doses
- Watch for orthostatic hypotension (more clinically significant than heart rate changes)
- Obtain baseline and follow-up ECGs in high-risk patients to assess QT interval and conduction abnormalities
- Be aware that doses above 150 mg/day may interfere with antihypertensive medications 6
Bottom line: Doxepin causes a mild increase in heart rate at therapeutic doses, not a decrease. Bradycardia only occurs in severe overdose situations as a pre-terminal event.