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Tobramycin, Inhaled Antibiotic, Eases Symptoms, Study in Off-label Use Finds

Off-label use of the inhaled antibiotic tobramycin lowered sputum production, and eased shortness of breath, and cough in people with bronchiectasis, a small real-world study found.

Although there was no significant improvement in lung function, the antibiotic eliminated almost half of the reported Pseudomonas aeruginosa infections and led to fewer hospitalizations.

Further studies are necessary for inhaled tobramycin to be established as standard therapy in bronchiectasis, the scientists said.

Pseudomonas aeruginosa represents about one-fifth of the bacterial species that are chronically found in the lungs of people with bronchiectasis.

Compared with other bacteria, this species’ presence is associated with a progressive loss of lung function, poor quality of life, more hospitalizations and exacerbations (a sudden worsening of symptoms), and increased mortality.

The use of inhaled antibiotics for treating bronchiectasis has been well investigated in cases secondary to cystic fibrosis (CF). However, research into non-cystic fibrosis bronchiectasis (NCFB) is relatively new; as such, evidence to support their use is limited, with inhaled antibiotics not currently approved to treat NCFB in the U.S. and Europe.

Researchers in Turkey examined the medical records of 27 bronchiectasis patients with P. aeruginosa infection who were treated off-label with tobramycin from 2014 through 2019, evaluating its efficacy and safety. Tobramycin is an antibiotic commonly used in eye drops to treat bacterial infections.

Data on 11 women and 16 men, with a mean age of 50.5, were selected for this study. CT scans revealed 23 (85%) patients had varicose bronchiectasis, in which the tubes leading to the lungs (bronchi) are irregular, and four (15%) had cylindrical bronchiectasis — when bronchi are enlarged and cylindrical. Bronchiectasis was found in both lungs in 21 (77.7%) patients.

The inflammatory lung disease chronic obstructive pulmonary disease (COPD) was observed in 24 (89%) people, and three (11%) had asthma. Overall, the mean FEV1/FVC ratio, which measures lung function as the volume of air blown out in one second (FEV1) over the total volume of air blown out (FVC), was low at 59%.

The most common symptom was sputum in 81.5%, followed by shortness of breath in 70.4%, and cough in 63%. None of the patients used sputum clearing devices, and shortness of breath was significantly more common in men. Of these 27 people, nine were smokers, all of whom were men with shortness of breath.

Inhaled tobramycin (300 mg) was administered twice daily in cycles of 28 days, followed by 28 days off for six months (one treatment period). In total, 21 patients completed one period, seven finished two periods, four completed three, and one patient finished four treatment periods.

Of those who completed treatment, 10 of 21 (47.6%) had negative bacterial cultures, with five remaining free from P. aeruginosa infection in the following year. The other five had a re-emerging infection. After the second treatment period, one patient (4.7%) developed antibiotic resistance.

Out of 22 participants with sputum complaints, 17 (77%) had a decrease in sputum production and colored (purulent) sputum, and eight of 19 patients reported lesser shortness of breath. A reduction in cough was observed in three (18%) of those who reported the symptom.

Before treatment, the frequency of hospitalizations was 1.24 each year, which significantly decreased to 0.52 per year after inhaled tobramycin.

Overall FEV1 was 40% one month before treatment and 44% after the last treatment period, with no statistical difference (normal 80% or higher). Likewise, no statistical difference was found in FVC before treatment (54%) compared with after treatment (55%). No such difference was seen in the inflammatory marker C-reactive protein or in white blood cells levels between pre- and post-treatment.

The most common side effect associated with inhaling tobramycin was shortness of breath, reported in five patients, with two discontinuing treatment.

“We believe that tobramycin inhalation therapy can be used for clinical improvement and sputum eradication in patients with NCFB,” the researchers wrote. “Moreover, it is well tolerated with rare side effects.”

“However, further studies are necessary to establish treatment standardization and determine the place of tobramycin inhalation therapy in the management of NCFB,” they added. “We believe that our study findings could be a guide for future studies and encourage the researchers who monitor these patients in clinical practice.”


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