Symptoms of an Allergic Reaction to Trazodone
True allergic reactions to trazodone are rare, but when they occur, they typically present with skin manifestations (rash, hives, itching), respiratory symptoms (shortness of breath, wheezing), swelling (face, lips, tongue), or in severe cases, cardiovascular symptoms (hypotension, rapid heartbeat) that require immediate medical attention. 1
Distinguishing True Allergy from Common Side Effects
Most adverse reactions to trazodone are side effects, not true allergic reactions. 2 It is critical to differentiate between these two categories:
True Allergic Reaction Symptoms
True allergic reactions are immune-mediated and typically occur within minutes to hours after drug exposure. 2 Key symptoms include:
- Skin manifestations: Generalized rash, extensive urticaria (hives), generalized itching, or angioedema (swelling of face, lips, tongue, or throat) 3
- Respiratory symptoms: Shortness of breath, wheezing, bronchospasm, or throat tightness 3
- Cardiovascular symptoms: Hypotension, tachycardia, or feeling faint 3
- Gastrointestinal symptoms (when combined with other allergic symptoms): Severe crampy abdominal pain, repetitive vomiting, or diarrhea 3, 2
Severity Grading of Allergic Reactions
Mild (Grade I): Isolated skin or mucosal signs such as generalized erythema, extensive urticaria, or angioedema without involvement of other organ systems 3
Moderate (Grade II): Multi-organ involvement with skin/mucosal signs plus moderate hypotension, tachycardia, moderate bronchospasm, or gastrointestinal symptoms 3
Severe (Grade III-IV): Life-threatening symptoms including severe hypotension, cardiac arrhythmias, severe bronchospasm, or cardiac/respiratory arrest 3
Common Side Effects That Are NOT Allergic Reactions
The FDA label for trazodone lists common adverse effects that should not be confused with allergic reactions. 1 These include:
- Drowsiness, sleepiness, or tiredness (very common) 1
- Dizziness or feeling unsteady 1
- Blurred vision 1
- Dry mouth 1
- Headache 1
- Nausea or vomiting (isolated, without other allergic symptoms) 1
- Constipation or diarrhea 1
Serious Non-Allergic Adverse Reactions
These are serious side effects but are NOT allergic reactions: 1
- Cardiac arrhythmias: QT prolongation, ventricular tachycardia, or irregular heartbeat 1, 4, 5
- Orthostatic hypotension: Dizziness when changing positions 1
- Priapism: Prolonged erection lasting more than 6 hours 1
- Serotonin syndrome: Agitation, hallucinations, coordination problems, fast heartbeat, tight muscles, fever, sweating 1
When to Seek Immediate Medical Attention
Call 911 or go to the emergency room immediately if you experience: 1
- Difficulty breathing or wheezing 3
- Swelling of the face, lips, tongue, or throat 3
- Widespread hives or rash with other symptoms 3
- Severe dizziness or fainting 3
- Chest pain or irregular heartbeat 1
- Signs of anaphylaxis (combination of respiratory, cardiovascular, and skin symptoms) 3
Clinical Pearls and Pitfalls
Common pitfall: Labeling drowsiness, dizziness, or isolated nausea as an "allergy" when these are expected pharmacological side effects. 2 This can lead to unnecessary avoidance of an effective medication. 2
Important distinction: If symptoms arise from a single organ system (e.g., only drowsiness or only mild nausea) without skin involvement or respiratory/cardiovascular changes, a true allergic reaction is unlikely. 3
Timing matters: True allergic reactions typically occur within minutes to hours after drug exposure, while side effects like drowsiness are expected and dose-related. 2
Documentation: The FDA label notes that "allergic reaction" occurred at <2% incidence in clinical trials, making true allergy uncommon. 1 Most reported adverse events are pharmacological side effects rather than immune-mediated allergic reactions. 6, 7