Amikacin causes little toxicity in carefully selected and closely monitored patients with non-tuberculous mycobacterial (NTM) disease but is less effective than previously thought, according to a case series published by Brisbane respiratory physicians.
Dr Claire Ellender, from the Princess Alexandra Hospital, and colleagues described 45 patients treated at three Brisbane hospitals between 2002 and 2012.
There were 25 with Mycobacterium intracellulare, 13 with Mycobacterium abscessus, six with Mycobacterium avium and one with Mycobacterium fortuitum.
They had been heavily pre-treated before receiving amikacin, and most had comorbidities including bronchiectasis and COPD.
The usual course of amikacin was 22 mg/kg/day given three times weekly for 8 weeks. It was used as part of multi-drug regimens that included antibiotics such as ethambutol, clarithromycin, rifampicin, azithromycin and clofazimine.
Eight patients experienced transient ototoxicity but only three had long-term hearing loss. There were no cases of nephrotoxicity and no long-term vestibulotoxicity.
“Sustained culture conversion at 6 months was only found in 17 patients (38%), however, the majority (34 patients, 76%) had a clinical response to treatment determined by an improvement in symptoms,” Dr Ellender wrote in Respirology.
No pretreatment patient or regimen factors were predictive of toxicity or treatment success in this small cohort.
“Lower treatment success rates were found than previous trials, suggesting there is a difficult balance in this patient group between treatment success and toxicities,” she said.
Pulmonary NTM disease is an increasingly common and challenging clinical problem. Mortality rates as high as 36% at 5 years have been reported, and five of the Brisbane patients died from NTM complications.
Amikacin has been used with caution in the past because of concerns about the well-documented risks of nephrotoxicity, ototoxicity and vestibulotoxicity, but the reported rates of these side effects have varied widely from 32% to just 1%.