Evaluation of Nail-fold Capillary Structures (Diameter and Tortuosity) in Carbamazepine-Treated Patients

Abstract

Carbamazepine is an anti-epileptic drug and used for treatment of several diseases such as epilepsy, neuropathic pain (neuralgia) and bipolar affective disorders. Several reports have shown vascular adverse drug effects of anti-epileptic drugs, including carbamazepine. Very few reports have been involved with micro-vascular (capillary) structural changes, which may be related to potential adverse drug reactions in patients with long-term therapy. The aim of this observational study was to evaluate nail-fold capillary structural changes in carbamazepine-treated patients in relation to serum carbamazepine concentrations and its apparent adverse drugs reactions. Patients from Chiangmai Neurological Hospital (N=60) were recruited and enrolled according to specific inclusion and exclusion criteria. All patients were treated with monotherapy of carbamazepine. Calibrated nail-microscope Dino-Lite® was employed to measure nail-fold capillary structural changes (i.e. arterial and venous diameters and tortuous index) at the proximal nail-fold. The measurement was performed in 1st and 2nd month after starting the treatment. Serum carbamazepine concentrations were also measured by fluorescene polarization immunoassay (Abbot Axsym System). Results showed that after one and two months of treatment the arterial loop diameters of the capillary were significantly decreased (9.05±1.07 [baseline] vs 8.88±1.10 and 8.78±1.15µm, p<0.001, respectively). Tortuous index was also found to be increased from baseline after treatment for one and two months; 1.64±0.32 µm vs 1.86±0.38 µm vs 1.94±0.36 µm, p<0.001, respectively. Correlation between % arterial loop diameter changes of the capillary and serum carbamazepine concentrations existed (r=-0.406, p<0.05), but not the turtuos index. Although frequency of adverse drug reactions was greater in patients whose serum carbamazepine concentrations ≥8 µg/mL, there was no established association of both % arterial loop diameter changes of capillary and tortuous index with apparent short-term adverse drug reactions.