Cutaneous silent periods are not affected by the antihistaminic drug cetirizine.
OBJECTIVE
Noxious digital nerve stimulation leads to transient suppression of the electromyographic activity in isometrically contracted hand muscles, known as the "cutaneous silent period" (CSP). To date, neurotransmitters potentially involved in mediating this electromyographic (EMG) suppression remain unknown. Anecdotal observation lead to the hypothesis that antihistaminic medication may counteract nociceptive EMG suppression, as CSPs in one male subject who was accustomed to CSP recordings were temporarily lost following ingestion of an antihistaminic drug for acute rhinitis. A second otherwise healthy male subject, who was on long-term cetirizine for allergic rhinitis, presented without clearly defined CSPs when volunteering for normal values.


METHODS
We undertook a systematic study in five healthy subjects (including the one with temporarily lost CSPs) who underwent serial CSP testing after ingestion of 10 mg cetirizine. CSPs were elicited in thenar muscles following digit II and digit V stimulation (20 times sensory threshold, 100 sweeps rectified and averaged) before and 90, 180, and 360 min following intake of medication.


RESULTS
CSP onset latency, CSP end latency and CSP duration, as well as the index of suppression did not change significantly following ingestion of 10 mg cetirizine. Repeat study in the subject with no clearly defined CSPs on long-term treatment revealed persistently absent CSPs after a 5-week withdrawal from cetirizine.


CONCLUSIONS
CSPs are not affected by therapeutic doses of the H1 antihistaminic cetirizine.


CONCLUSIONS
Our findings suggest that histamine plays no major role as a neurotransmitter of CSPs.
Department of Neurology, Hochzirl Hospital, A-6170 Zirl, Austria. markus.kofler@i-med.ac.at
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M
Kofler
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Kumru
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Stetkarova
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Rüegg
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Fuhr
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Leis
D000328:Adult; D017332:Cetirizine / Q000494:pharmacology*; D004576:Electromyography; D005260:Female; D006225:Hand / Q000294:innervation / Q000502:physiology*; D006634:Histamine H1 Antagonists / Q000494:pharmacology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology*; D009431:Neural Conduction / Q000187:drug effects / Q000502:physiology; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology; D010525:Peripheral Nerves / Q000187:drug effects / Q000502:physiology; D011930:Reaction Time / Q000187:drug effects / Q000502:physiology; D011984:Sensory Receptor Cells / Q000187:drug effects* / Q000502:physiology*
D006634:Histamine H1 Antagonists; D017332:Cetirizine