Advantages of Azithromycin Over Erythromycin in Improving the Gastric Emptying Half-Time in Adult Patients With Gastroparesis

BACKGROUND/AIMS: Current therapy for gastroparesis with prokinetic agents is limited by options and side effects. One macrolide, erythromycin (ERY), is associated with possible sudden cardiac death from QT prolongation due to P450 iso-enzyme inhibition. An alternative, azithromycin (AZI), lacks P450 inhibition. We compared the effect on gastric emptying half-times (t½) between AZI and ERY in patients diagnosed with gastroparesis by gastric emptying scintigraphy. METHODS: Patients stopped medications known to affect gastric emptying prior to the study, and then ingested 1 scrambled egg meal labeled with 18.5-37 MBq of technetium-99m sulfur colloid followed by continuous imaging for 120 minutes, at 1 minute per frame. A simple linear fit was applied to the rate of gastric emptying, and gastric emptying t½ was calculated (normal = 45-90 minutes). At 75-80 minutes, if the stomach had clearly not emptied, patients were given either ERY (n = 60) or AZI (n = 60) 250 mg IV and a new post-treatment gastric emptying t½ was calculated. RESULTS: Comparison of gastric emptying t½ showed a similar positive effect (mean gastric emptying t½ for AZI = 10.4 ± 7.2 minutes; mean gastric emptying t½ for ERY = 11.9 ± 8.4 minutes; p = 0.30). CONCLUSIONS: AZI is equivalent to ERY in accelerating the gastric emptying of adult patients with gastroparesis. Given the longer duration of action, better side effect profile and lack of P450 interaction for AZI as compared with ERY, further research should evaluate the long term effectiveness and safety of AZI as a gastroparesis treatment.