Maximum Percent Decrease Research Articles

Cigarette smoking and chlorpromazine disposition and actions.

Chlorpromazine, 75 mg, was taken by eight cigarette smokers and nine nonsmokers. Mean maximum percent decrease in mean blood pressure with change in position from lying to standing during the first 10 hr after chlorpromazine was 46% greater in nonsmokers than in smokers. Of the eight smokers, six did not become sleepy after chlorpromazine, one became slightly sleepy, and one fell asleep. Of the nine nonsmokers, three became slightly sleepy, one moderately sleepy, and five fell asleep. Mean peak plasma concentration of chlorpromazine was 24% lower and mean area under the plasma concentration-time curve (AUC) was 36% lower in smokers than in nonsmokers. There was no correlation between these plasma level parameters and either the degree of sleepiness or the degree of orthostatic hypotension in the subjects. The relatively small differences between cigarette smokers and nonsmokers in AUCs and peak plasma levels for chlorpromazine, combined with the lack of relationship between these plasma level parameters, the occurrence of drowsiness, and the magnitude of orthostatic hypotension in our subjects make it unlikely that cigarette smoking influenced these effects of chlorpromazine by enhancing its overall metabolism.

Plasma clonidine in relation to blood pressure, catecholamines, and renin activity during long-term treatment of hypertension.

Eight patients with essential hypertension were treated with 50 microgram oral clonidine four times daily for 4 wk followed by 75 to 150 microgram four times daily for another 4 to 16 wk. Before treatment and at the end of each treatment period the patients were hospitalized and their plasma clonidine concentrations (P-CLON) were determined repeatedly during one dosage interval. The relationship of P-CLON to blood pressure, heart rate, plasma norepinephrine (PNE), and plasma renin activity (PRA), as well as to conventional kinetic parameters, was calculated. With the two dosages used the half-life (t 1/2 s) of clonidine absorption were 1.05 and 0.83 hr, the biological t 1/2 s 8.7 and 7.9 hrs, and the total oral clearances 4.7 and 5.0 ml X min-1 X kg-1. The log of P-CLON correlated with the maximum percentage decrease of mean arterial blood pressure (MAP) (r = 0.91, P less than 0.001) in five patients, whereas in three patients there was no further decrease of MAP after increase of plasma clonidine level. The logarithm of P-CLON correlated with percentage reduction of PNE (r = 0.67, P less than 0.01). In six patients in whom clonidine induced a reduction of PRA, there was a relationship between log P-CLON and percentage PRA reduction (r = 0.91, P less than 0.001) and also between the percentage PRA and PNE reduction (r = 0.74, P less than 0.01).

Effect of Elastic Compression on Venous Hemodynamics in Postphlebitic Limbs

To determine whether elastic compression alters the venous hemodynamics in the postphlebitic limb, we measured venous pressure patterns in 11 postphlebitic limbs with and without elastic compression stockings. Following cannulation of a dorsal vein of the foot, the patients underwent measurements of basal resting pressure, maximum percent decrease in venous pressure with exercise (delta VPex), peak systolic venous pressure during exercise (SVPmax), the amplitude of the pressure swing, and venous return time. Elastic compression did not alter basal resting pressure, delta VPex, or venous return time. By contrast, SVPmax decreased from 139 +/- 0.3 mm Hg to 11 +/- 8 mm Hg with elastic compression. If venous ulcers are related to the high pressure developed in the superficial veins during calf muscle systole, then elastic compression may be beneficial by decreasing systolic venous pressure and its subsequent deleterious consequences.

Effect of elastic compression on venous hemodynamics in postphlebitic limbs

To determine whether elastic compression alters the venous hemodynamics in the postphlebitic limb, we measured venous pressure patterns in 11 postphlebitic limbs with and without elastic compression stockings. Following cannulation of a dorsal vein of the foot, the patients underwent measurements of basal resting pressure, maximum percent decrease in venous pressure with exercise (ΔVP_ex), peak systolic venous pressure during exercise (SVP_max), the amplitude of the pressure swing, and venous return time. Elastic compression did not alter basal resting pressure, ΔVP_ex, or venous return time. By contrast, SVP_maxdecreased from 139±0.3 mm Hg to 111±8 mm Hg with elastic compression. If venous ulcers are related to the high pressure developed in the superficial veins during calf muscle systole, then elastic compression may be beneficial by decreasing systolic venous pressure and its subsequent deleterious consequences. (<i>JAMA</i>242:2766-2768, 1979)

Sensory Irritation of Select Experimental Photochemical Oxidants

Groups of male Swiss-Webster mice were exposed to photochemical oxidant mixtures generated by reacting various hydrocarbons with nitrogen dioxide in the presence of ultraviolet light while their respiratory rates were monitored. The hydrocarbons used were 1,3-butadiene, 1-butene, cis-2-butene, ethylene, propylene, n-butane, and ethane. The initial hydrocarbon concentrations ranged from .4 to 18 ppm, with the initial nitrogen dioxide concentration being one-third that of the initial hydrocarbon concentration. New groups (four mice per group) were exposed for 5 min at 0, 1, 2, 3, and 4 hr of ultraviolet irradiation. Dose-response curves for each hydrocarbon were developed by plotting the maximum percent decrease in respiratory rate observed during the 4 hr of irradiation of each mixture as a function of the initial hydrocarbon concentration present. The percent decrease in respiratory rate in mice was chosen as an index of the sensory irritation of the upper respiratory tract for each mixture. The results showed that the potency of the photochemical oxidant mixtures generated from the hydrocarbons to be propylene greater than 1,3,-butadiene = 1-butene=cis-2-butene greater than ethylene. When ethane or n-butane was used, no decrease in respiratory rate was observed. These results are compatible with the data obtained in human volunteer studies. Guidelines for relating the percent decrease in respiratory rate in mice to human reactions are presented.

Sensory Irritation and Incapacitation Evoked by Thermal Decomposition Products of Polymers and Comparisons with Known Sensory Irritants

A decrease in respiratory rate in mice during exposure to irritating airborne chemicals has been utilized as a response parameter to characterize the degree of upper respiratory tract irritation (sensory irritation) to the thermal decomposition products of various polymers. These included polystyrene, polyvinyl chloride, flexible polyurethane foam, polytetrafluorethylene, a fiber glass reinforced polyester resin, and Douglas Fir. Each of the materials was thermally decomposed in a low-mass vertical furnace in an air atmosphere at a programmed heating rate of 20 degrees C/min. Mice, in groups of four, were exposed to graded concentrations of the thermal decomposition products of each of the above materials. Dose-response curves were obtained by utilizing the maximum percent decrease in respiratory rate as the response parameter during each exposure. Comparison of these dose-response curves with other sensory irritants such as chlorine, ammonia, hydrogen chloride, sulfur dioxide, and toluene diisocyanate gave an indication of the sensory irrtation potential of the thermal decomposition products of these various polymers versus that of well-known single airborne chemical irritants. Total stress and incapacitation of the organism during exposure to sensory irritants such as from the thermal decomposition products of synthetic polymers is discussed.

Sensory irritation evoked by the thermal decomposition products of plasticized poly(vinyl chloride)

AbstractA decrease in respiratory rate in mice during exposure to irritating airborne chemicals has been utilized as a response parameter to characterize the degree of upper respiratory tract irritation (sensory irritation) to the thermal decomposition products of plasticized poly(vinyl chloride). The plasticized poly(vinyl chloride) was placed in a low mass vertical furnace and thermally decomposed in an air atmosphere at a programmed heating rate of 20°C min−1. The thermogravimetric study of the plasticized poly(vinyl chloride) demonstrated that two distinct weight loss fractions occurred during the decomposition process. Groups of four male swiss‐webster mice were exposed to the thermal decomposition products of the first weight loss fraction in the range 0.03–0.77 mg l−1 and to the second weight loss fraction in the range 0.03–0.38 mg l−1. Dose‐response curves were plotted by utilizing the maximum percent decrease in respiratory rate during each exposure as the response parameter. Comparison of these curves to a dose‐response curve for hydrogen chloride showed that both the first and second weight loss fraction of plasticized poly(vinyl chloride) were more potent than hydrogen chloride in terms of sensory irritation. From these dose‐response relationships qualitative and quantitative predictions of human responses to the thermal decomposition products of plasticized.