[Potentiation of deltamethrin toxicity by organophosphorus insecticides]. / Potentialisation de la toxicité de la deltaméthrine par les insecticides organophosphorés.

There is a potential hazard in mixed intoxications by pyrethroids and organophosphate insecticides, due to the fact that low toxicity of pyrethroids on mammals is chiefly due to quick cleavage of molecule by esterases, which can be thwarted by esterase inhibitors. We have developed a method in order to measure the duration and the intensity of potentiation of deltamethrin by a variety of organophosphate compounds. It was demonstrated that some of them (azinphos, dichlorvos, dimethoate, fenitrothion, omethoate) induce an increase of toxicity of deltamethrin. But, the total toxicity of association of Deltamethrin with Dimethoate, Fenitrothion, is weak, and does not prohibit their use. Others (methyl-parathion, acephate, phosphamidon, monocrotophos) have no such effects, even if they have a very high intrinsic toxicity. Cholinesterase inhibitors of the carbamate group are ineffective. It is suggested that the potentiation is mainly in relation with the kinetic of esterase inhibition, which is different, and specific to each organophosphate compound. So, it is essential that a specific toxicological measurement must be performed with any different insecticide, in order to anticipate the danger of a mixed intoxication by pyrethroids and organophosphates.

Effect on postural sway of various benzodiazepine tranquillizers.

The effects of various benzodiazepine tranquillizers (clobazam 20 mg, bromazepam 6 mg and lorazepam 2 mg) were investigated by posturography in 16 subjects in a controlled trial. Twelve received each of the three anxiolytics for 1 week in a cross-over design, four received placebo for 1 week during the three successive treatment periods. A pharmacodynamic study was carried out after the first administration, and another assessment was done after 1 week of treatment. The first administration of lorazepam caused the most marked disturbances of body sway (increase of spectral energies, length and amplitude of the stabilogram). The first administration of bromazepam was also accompanied by an increase of the posturographic parameters, although less marked. Administration of clobazam did not produce any impairment of equilibrium, indicating that it is devoid of any sedative effect measurable by posturography. No changes of the postural sway can be detected on the measurement recorded 10 h after the last dose of 1 week's treatment.

Dose-response relationship of vindeburnol based on spectral analysis of posturographic recordings.

The dose-response relationship of vindeburnol has been investigated by assessing postural activity in a population of elderly patients, using posturography, an objective method for measuring balance. A controlled double blind trial was done in two periods: during the first week each patient received placebo, and during the second week either placebo or vindeburnol 30, 60 or 90 mg/d was given. Subjects underwent three posturographic recordings at weekly intervals (prior to treatment, after one week on placebo and after one week of treatment). There was no placebo effect. A significant decrease in the sagittal and lateral energies of body sway was found after vindeburnol, which indicates an improvement in balance. The improvement was proportional to the daily dose of vindeburnol.

[Electroplethysmographic study of nitroglycerin microcapsule preparation at two concentrations: 2.5 and 7.5 mg (author's transl)]. / Etude par pléthysmographie électrique d'une nitroglycérine microencapsulée dosée à 2,5 et 7,5 mg.

In a double-blind, cross-over study involving 15 subjects (10 healthy volunteers and 5 patients with chronic coronary disease) the authors have compared the activity of two nitroglycerin microcapsule preparations containing 2.5 and 7.5 mg respectively. The hemodynamic effects were assessed by electroplethysmography, which is based on variations of impedance in the precordial area. The method records plethysmographic changes in the aorta and measures parameters exploring ventricular stroke. Both concentrations were found to be active. The effects lasted about 1 to 3 hours with the 2.5 mg preparation and more than 4 hours with the 7.5 mg preparation. The response to the 7.5 mg dose was approximately 50% greater than that to the 2.5 mg dose. These findings were supported by the occurence of headaches of six hours duration in 3 out of the 10 healthy subjects.