There are two main uses of azithromycin:
As a conventional antibiotic (see section 6.2a) for treatment of respiratory infections especially if Mycoplasma or Chlamydia are being considered.
As a long term anti-inflammatory agent, although it’s mechanism of action is unknown. Studies show improvement in FEV1 (median 5.5%) and reduction of oral antibiotic usage. It is believed to be effective in those with and without chronic Pseudomonas infection.
Criteria for long term use: Very similar to those for DNase (see section 6.4) and should include those not benefiting from a 3 month trial of DNase.
Dosage: 250 mg once daily (<40kg) or 500 mg once daily (≥40kg) three times a week (Mon Wed Fri)
Judgement of response: Onset of action is slow (at least 2 months) and a minimum 4, preferably 6 month trial is required. If there has been a beneficial response then we recommend reducing the dosing frequency to Monday/Wednesday/Friday only.
Side Effects: Theoretically liver function abnormalities and reversibletinnitus although only one transient LFT abnormality was observed during the study. Liver function tests should be performed at any time blood is being taken for other reasons and at annual assessment. Use of azithromycin and erythromycin (prokinetic) long term should be avoided due to potential additive side effects. There are some anxieties in the literature about Azithromycin acting as a single agent NTM treatment, although examining our own data and the US study suggests no increased risk of isolating NTM in those on AZM, indeed we found that long term AZM may reduce the NTM risk.
When AZM is started, consider stopping prophylactic flucloxacillin or co-amoxiclav, unless there is a good reason to continue, ie patient is known to have macrolide-resistant organisms.