Inhaled Colistin Dosing for Bronchiectasis with Chronic Pseudomonas Aeruginosa Infection
The recommended dose of inhaled colistin is 1 million units (MU) twice daily, which is equivalent to approximately 80 mg of colistimethate sodium twice daily (160 mg total daily dose). 1
Standard Dosing Regimen
Inhaled colistin should be administered at 1 MU (approximately 80 mg colistimethate sodium) twice daily through an appropriate nebulizer device such as the I-neb 1
The European consensus guidelines confirm this dosing: 2 mega units (MU) total per day, divided as 1 MU twice daily 1
This translates to approximately 160 mg of colistimethate sodium per day (80 mg per dose, twice daily) 1
Critical Considerations for Your Patient
Renal Impairment Adjustment
Inhaled colistin does NOT require dose adjustment for renal impairment because systemic absorption is minimal with nebulized administration 1. This is a crucial advantage over intravenous colistin, which requires significant dose reduction in renal dysfunction 2.
The British Thoracic Society specifically states to avoid long-term inhaled aminoglycosides if creatinine clearance is <30 mL/min, but this precaution applies primarily to inhaled gentamicin, not colistin 1
Monitoring by serum levels is not feasible for inhaled colistin 1
Drug Interaction with Sotalol
There are no significant pharmacokinetic interactions between inhaled colistin and sotalol because inhaled colistin has minimal systemic absorption 1. However, both drugs can potentially prolong QT interval through different mechanisms, so baseline ECG monitoring is prudent.
Preparation and Administration
Prepare an isotonic solution by dissolving 2 MU of colistin in 3 mL sterile water and 3 mL physiological saline (0.9% NaCl) to create a total volume of 6 mL for nebulization 1. This isotonic preparation minimizes bronchoconstriction risk 1.
Use a nebulizer that produces particles in the 2-5 μm range to ensure adequate lower airway deposition 1
Administer a bronchodilator before colistin nebulization to prevent drug-induced bronchoconstriction 1
Monitor lung function before and immediately after the first few doses 1
Treatment Duration and Monitoring
Continue treatment for at least 6 months before assessing efficacy, as clinical benefits may take time to manifest 1, 3
Review patients every 6 months to assess efficacy, toxicity, and continuing need 1, 4, 5
Monitor sputum cultures regularly, though in vitro resistance may not correlate with clinical efficacy 1, 4
Common Pitfalls to Avoid
Do not use hypotonic or hypertonic solutions as they can cause bronchoconstriction and airway inflammation 1. Always prepare isotonic solutions as described above.
Do not assume systemic toxicity will occur with inhaled administration—nephrotoxicity and ototoxicity are rare with properly dosed inhaled colistin, unlike intravenous formulations 1, 6. However, one case report documents vestibular toxicity in a patient with renal failure receiving inhaled tobramycin, suggesting caution in severe renal impairment 7.
Ensure adequate adherence as the clinical trial data showing benefit (168 days vs 103 days to exacerbation) was only significant in patients taking ≥81% of prescribed doses 1.
Expected Outcomes
With proper dosing and adherence, expect: