RESUMEN
OBJECTIVES: The treatment of neuropathic pain is mainly based on antiepileptics, tricyclic antidepressants, and opiates. These drugs have important side effects disturbing the patient's quality of life. Mirtazapine (MTZ) is a new and well-tolerated tricyclic antidepressants with both monoaminergic and opioid properties that might favorably influence pain. The aim of this study was to assess whether MTZ can reduce the pain induced by a standardized stimulus presented to healthy human participants. The nociceptive flexion reflex (NFR) to an electric stimulus was chosen to determine the pain threshold. METHODS: The effect of MTZ compared to placebo was assessed on 10 healthy participants in a double-blinded cross-over design. The NFR was measured the day after a single oral dose of drug (30 mg) or placebo. RESULTS: A significant increase in upper limb (+29%, P=0.006) NFR threshold was observed. DISCUSSION: MTZ increases the pain tolerance in healthy participants. The potential benefit of this effect on pain should be investigated more thoroughly in chronic neuropathic pain patients. The NFR might serve as an additional tool for the monitoring of these patients.
Asunto(s)
Analgésicos/administración & dosificación , Antidepresivos Tricíclicos/administración & dosificación , Mianserina/análogos & derivados , Neuralgia/tratamiento farmacológico , Enfermedades del Sistema Nervioso Periférico/tratamiento farmacológico , Adulto , Analgésicos/efectos adversos , Antidepresivos Tricíclicos/efectos adversos , Estudios Cruzados , Método Doble Ciego , Esquema de Medicación , Estimulación Eléctrica/efectos adversos , Femenino , Humanos , Pierna/inervación , Pierna/fisiopatología , Masculino , Mianserina/administración & dosificación , Mianserina/efectos adversos , Persona de Mediana Edad , Mirtazapina , Neuralgia/fisiopatología , Nociceptores/efectos de los fármacos , Nociceptores/fisiología , Dimensión del Dolor/efectos de los fármacos , Umbral del Dolor/efectos de los fármacos , Umbral del Dolor/fisiología , Nervios Periféricos/efectos de los fármacos , Nervios Periféricos/fisiopatología , Enfermedades del Sistema Nervioso Periférico/fisiopatología , Efecto Placebo , Tiempo de Reacción/efectos de los fármacos , Tiempo de Reacción/fisiología , Reflejo/efectos de los fármacos , Reflejo/fisiología , Resultado del TratamientoRESUMEN
BACKGROUND AND PURPOSE: A right-to-left shunt can be identified by contrast transcranial Doppler ultrasonography (c-TCD) at rest and/or after a Valsalva maneuver (VM) or by arterial blood gas (ABG) measurement. We assessed the influence of controlled strain pressures and durations during VM on the right-to-left passage of microbubbles, on which depends the shunt classification by c-TCD, and correlated it with the right-to-left shunt evaluation by ABG measurements in stroke patients with patent foramen ovale (PFO). METHODS: We evaluated 40 stroke patients with transesophageal echocardiography-documented PFO. The microbubbles were recorded with TCD at rest and after 4 different VM conditions with controlled duration and target strain pressures (duration in seconds and pressure in cm H2O, respectively): V5-20, V10-20, V5-40, and V10-40. The ABG analysis was performed after pure oxygen breathing in 34 patients, and the shunt was calculated as percentage of cardiac output. RESULTS: Among all VM conditions, V5-40 and V10-40 yielded the greatest median number of microbubbles (84 and 95, respectively; P<0.01). A significantly larger number of microbubbles were detected in V5-40 than in V5-20 (P<0.001) and in V10-40 than in V10-20 (P<0.01). ABG was not sensitive enough to detect a shunt in 31 patients. CONCLUSIONS: The increase of VM expiratory pressure magnifies the number of microbubbles irrespective of the strain duration. Because the right-to-left shunt classification in PFO is based on the number of microbubbles, a controlled VM pressure is advised for a reproducible shunt assessment. The ABG measurement is not sensitive enough for shunt assessment in stroke patients with PFO.