How Inhaled Corticosteroids Cause Oral Thrush
Inhaled corticosteroids cause oral candidiasis by suppressing local immune responses in the oropharynx, reducing salivary IgA levels and allowing Candida species to proliferate unchecked. 1, 2
Mechanism of Pathogenesis
The anti-inflammatory effects of corticosteroids decrease lymphocytic signaling and local immunological reactions that normally control fungal populations in the oral cavity. 1 Specifically, inhaled corticosteroids can decrease salivary total IgA—a critical component of mucosal immunity—though host factors also play an important role in whether clinical candidiasis develops. 2 The local immunosuppression created by corticosteroid deposition in the mouth and throat creates an environment where Candida species can colonize and cause symptomatic infection. 1, 3
Incidence and Risk Factors
The overall incidence of oral candidiasis with inhaled corticosteroids is substantial:
- Overall 3-year occurrence rate: 7% in seniors using inhaled steroids 4
- Odds ratio of 2.65 (95% CI 2.03-3.46) for developing oral candidiasis compared to non-users 5, 1
- One case of oral candidiasis for every 21 patients treated 5
Specific Risk Factors That Increase Thrush Development:
- Higher doses of inhaled corticosteroids—risk increases dose-dependently 6, 4
- Longer duration of exposure to inhaled steroids 4
- Concurrent use of oral systemic corticosteroids 4
- Use of antibiotics 4
- Having three or more prescribers (likely reflecting polypharmacy) 1, 4
- History of using both high and low strengths of inhaled corticosteroids 4
- Metered-dose inhalers (MDIs) carry higher risk than dry-powder inhalers (DPIs)—5-fold vs 3-fold increased risk compared to placebo 6
- Fluticasone appears to carry higher risk than beclomethasone, with Candida colonization increasing dose-dependently with fluticasone 7
Prevention Strategies
The most effective prevention is proper mouth rinsing technique immediately after each inhaled corticosteroid use. 8, 1
Specific Prevention Measures:
- Rinse mouth at least twice and spit after each ICS use—this is the single most important preventive measure 8
- Use a large-volume spacer or valved holding chamber with MDIs—this reduces oropharyngeal deposition by 50-70% 8, 9
- Time ICS use just before tooth brushing twice daily—naturally incorporates thorough mouth rinsing 8
- Use the minimum effective dose to control asthma symptoms 1
- Limit duration of high-dose therapy when possible 1
Common Pitfall to Avoid:
Never allow patients to use MDIs without a spacer device, as this maximizes oropharyngeal deposition and dramatically increases thrush risk. 8, 9 Many patients skip mouth rinsing because they don't understand its importance—explicit instruction is essential. 8
Treatment When Thrush Develops
If oral candidiasis develops despite preventive measures:
Mild Disease:
- Clotrimazole lozenges 10 mg five times daily for 7-14 days 1
- Miconazole mucoadhesive buccal tablets 50 mg once daily for 7-14 days 1
- Amphotericin B gargle (1:50 dilution) is effective in most patients with ICS-associated candidiasis 7
Moderate to Severe Disease:
- Fluconazole 100-200 mg orally daily for 7-14 days 1
Critical Management Point:
If fungal infection develops, suspend corticosteroids and initiate antifungal therapy before considering resuming corticosteroid treatment. 1 However, in practice with asthma patients, you can often continue the inhaled steroid while treating the thrush if asthma control requires it—just ensure rigorous mouth rinsing and consider switching to a DPI or adding a spacer if not already using one. 6, 7
Device-Specific Considerations
The delivery device significantly impacts thrush risk:
- MDIs (both HFA and CFC formulations) carry 5-fold increased risk of oral candidiasis versus placebo 6
- DPIs carry 3-fold increased risk versus placebo 6
- Adding a spacer to MDI reduces risk substantially by decreasing oropharyngeal deposition 8, 9
Special Populations at Higher Risk
Patients with the following conditions require extra vigilance: