Influence of calcium channel blocker drugs in neuromuscular transmission.
OBJECTIVE
Calcium channel blockers are commonly used in some cardiovascular disorders. These drugs can act at neuromuscular transmission, at both pre- and postsynaptic levels and may produce neuromuscular dysfunction. Therefore, they may result in misdiagnosis in electrophysiological testing of healthy subjects. This study aimed to investigate the influence of calcium channel blockers on neuromuscular transmission, using single fiber electromyography, in subjects who were healthy excepting controlled arterial hypertension condition.


METHODS
Single fiber electromyography during voluntary contraction of the extensor digitorum communis muscle, nerve conduction studies of upper and lower extremities, and concentric needle electromyography of the extensor digitorum communis were performed on 16 verapamil users, 16 amlodipine users, and 16 age-matched normal controls. Twenty potential pairs were recorded from each subject. Twenty individual jitter values and a mean jitter value were calculated for each subject. Both mean jitter values and numbers of abnormal individual jitter values were compared in verapamil and amlodipine users versus normal controls.


RESULTS
Eight of 16 verapamil users and 7 of amlodipine users showed evident neuromuscular transmission abnormalities by single fiber electromyography. Two subjects from verapamil and one subjects from amlodipine users group had borderline dysfunction of neuromuscular transmission.


CONCLUSIONS
These results suggest that both verapamil and amlodipine impair neuromuscular transmission in subjects without neuromuscular disease.


CONCLUSIONS
The effects of verapamil and amlodipine are at a level, which may cause misinterpretation of single fiber electromyography studies carried out to investigate neuromuscular junction disorders.
Ozkul
Yasar
Y
Harran University, Faculty of Medicine, Department of Neurology, Arastirma Hastanesi, Noroloji Klinigi, 63100 Sanliurfa, Turkey. yasarozkul@yahoo.com
D000328:Adult; D017311:Amlodipine / Q000009:adverse effects* / Q000627:therapeutic use; D002121:Calcium Channel Blockers / Q000009:adverse effects* / Q000627:therapeutic use; D004576:Electromyography; D005260:Female; D005385:Fingers; D006801:Humans; D006973:Hypertension / Q000188:drug therapy* / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000187:drug effects; D018482:Muscle, Skeletal / Q000294:innervation / Q000503:physiopathology; D009469:Neuromuscular Junction / Q000503:physiopathology*; D009435:Synaptic Transmission / Q000187:drug effects*; D014700:Verapamil / Q000009:adverse effects* / Q000627:therapeutic use
D002121:Calcium Channel Blockers; D017311:Amlodipine; D014700:Verapamil