Objective: To investigate muscle function in patients with severe myalgia resulting from fluoroquinolone (FQ) treatment. We used histology, in vitro contracture tests (IVCTs), and (31)P magnetic resonance spectroscopy ((31)P MRS) to explore muscle contraction and metabolism.
Methods: We studied 3 patients with myalgia, hyperalgia tendinopathy, and arthralgia following FQ treatment and 3 normal subjects after taking FQs. Results were compared with those of a control group of 9 subjects free of any muscle disease and not taking FQs. Muscle biopsies were performed on the left biceps, and IVCTs were performed in accordance with the protocol recommended by the European Malignant Hyperthermia Group. (31)P MR spectra of forearm flexor muscles were recorded at 4.7T throughout a rest-exercise-recovery protocol.
Results: (31)P MRS showed a significant reduction of pH changes measured at the end of exercise and a faster rate of proton efflux measured during recovery in all patients. IVCTs diagnosed 1 patient as being susceptible to malignant hyperthermia. No specific histologic anomalies were observed in muscle biopsy samples, which showed normal mitochondria.
Conclusion: The adverse effects recorded in the 3 patients are related to a preexisting muscular anomaly revealed by FQ treatment.