Why is Dynapar (diclofenac) contraindicated in patients with asthma?

Why Dynapar (Diclofenac) is Contraindicated in Asthmatics

Dynapar (diclofenac) is contraindicated in asthmatics because NSAIDs can trigger severe, potentially life-threatening bronchospasm and acute asthma exacerbations in approximately 10% of adults with asthma, particularly those with high-risk features such as severe asthma, nasal polyps, or chronic rhinosinusitis. 1

Mechanism and Clinical Syndrome

NSAIDs like diclofenac inhibit cyclooxygenase-1 (COX-1), which can precipitate a condition known as aspirin-exacerbated respiratory disease (AERD)—the triad of asthma, chronic rhinosinusitis with nasal polyposis, and acute respiratory reactions after NSAID intake. 2 This syndrome is characterized by:

• Chronic eosinophilic airway inflammation that becomes acutely exacerbated by NSAIDs 2
• Acute hypoxemic respiratory failure requiring emergency treatment with oxygen, nebulized bronchodilators, and systemic corticosteroids 2
• Progressive disease despite guideline-based asthma treatment and NSAID avoidance 2

The mechanism is pseudoallergic (non-immunologic) rather than true allergic, meaning it occurs through pharmacologic pathways rather than IgE-mediated reactions. 3 This makes it unpredictable and potentially severe even on first exposure in susceptible individuals.

High-Risk Patient Populations

Patients with asthma who exhibit any of the following features should be considered at particularly high risk for NSAID-induced bronchospasm: 1

• Severe asthma requiring high-intensity controller therapy
• Nasal polyps (polyposis nasi)
• Chronic rhinosinusitis or pansinusitis
• Known prior NSAID intolerance

These patients should avoid NSAIDs entirely or use them only under close medical supervision with formal aspirin provocation testing beforehand. 1

Clinical Severity and Real-World Evidence

The contraindication is based on substantial clinical evidence:

• Approximately 10% of adults with asthma experience respiratory deterioration with NSAIDs, with a smaller proportion of children affected 1
• Severe, sometimes life-threatening bronchospasm can occur, as documented in case reports of acute asthma exacerbations requiring hospitalization after diclofenac use 2
• Paradoxical bronchial constriction from NSAIDs is clinically recognized as one of the most important forms of drug-induced bronchial asthma 3

A documented case illustrates the severity: a 60-year-old man with nasal polyposis and pansinusitis developed hypoxemic respiratory failure requiring oxygen, nebulized bronchodilators, and prednisolone after taking diclofenac preoperatively, recovering only after one day of intensive treatment. 2

Clinical Recommendations

For patients with asthma who have never used NSAIDs and lack high-risk features:

• Treat as potentially intolerant to NSAIDs 1
• Use NSAIDs only under medical supervision 1
• This conservative approach is necessary due to lack of experimental evidence to predict safety 1

For patients with known NSAID intolerance or high-risk features:

• Strongly avoid all NSAID derivatives including diclofenac 3
• Document the contraindication in the patient's emergency passport or medical alert system 3
• Consider formal aspirin provocation testing only if therapeutic NSAID use is absolutely necessary 1

Important caveat: NSAID intolerance can develop late in life, even in patients who previously tolerated these medications without problems. 1 Therefore, ongoing vigilance is required even in patients with prior safe NSAID use.

Alternative Analgesic Options

Paracetamol (acetaminophen) remains the safest alternative for most asthmatic patients:

• Only a small proportion of NSAID-intolerant asthmatics experience short-lived respiratory deterioration with high-dose paracetamol 1
• This reaction is uncommon and has not been implicated in life-threatening reactions 1
• Routine warnings about paracetamol in asthma are not warranted, though clinicians should remain alert to potential symptom worsening in individual patients 1

Key Clinical Pitfall

The most critical pitfall is assuming that patients without prior NSAID exposure or obvious high-risk features are safe to receive diclofenac. The pseudoallergic mechanism means reactions can occur unpredictably, and the consequences can be severe enough to require emergency intervention. 2, 3 The safest approach is to avoid NSAIDs in all asthmatics unless there is documented prior tolerance with regular use, and even then, patients should be warned about potential late-onset intolerance. 1