Effective duration, contrast

Adverse effects of cocaine include constricted peripheral blood vessels, dilated pupils, and increased body temperature, heart rate, and blood pressure. Cocaine induces several immediate euphoric effects, such as hyperstimulation, reduced fatigue, and mental clarity, all of which depend on the administration route. The faster the absorption of cocaine, the more severe the effects. In contrast, faster absorption limits the duration of action. For example, the effect from snorting cocaine may last 15 to 30 minutes, whereas effects from smoking may last 5 to 10 minutes. Increased use can reduce the period of stimulation, as addicted humans may develop tolerance. In rare instances, sudden death may occur on the first use of cocaine or unexpectedly thereafter. 

Awai K, Hiraishi K, Hori S (2004) Effect of contrast material injection duration and rate on aortic peak time and peak enhancement at dynamic CT involving injection protocol with dose tailored to patient weight. Radiology 230 142-150... 

Two intermediate-duration studies in rats in which lead was administered mixed in the food as acetate, oxide, sulfide, and lead contaminated soil identified NOAELS of 5 mg lead/kg/day (Dieter et al. 1993) and 6.4 mg lead/kg/day (Freeman et al. 1996) for food intake for all lead forms tested. These doses were the highest doses tested. A 90-day study in rats reported no effects of lead exposure on water intake in rats administered doses of approximately 38 mg lead/kg/day as acetate via drinking water (Kala and Jadhav 1995a). In contrast, rats given a much higher dose of lead acetate in the water (0.6% corresponding to approximately 502 mg lead/kg/day) for 14-50 days showed a 17-20% decrease in water intake (Ronis et al. 1996). 

The answer is d. (Hardman, pp 865-867.) Lidocaine usually shortens the duration of the action potential and, thus, allows more time for recovery during diastole. It also blocks both activated and inactivated Na channels. This has the effect of minimizing the action of lidocaine on normal myocardial tissues as contrasted with depolarized ischemic tissues. Thus, lidocaine is particularly suitable for arrhythmias arising during ischemic episodes such as myocardial infarction (Ml). 

Szara and co-workers (221,223,225) noted psychotomimetic activity for N,N-diethyltryptamine (DET 38) at a dose of 1 mg/kg. In at least one study (223), the effects of DET were found to be unpleasant. In a study involving 71 subjects, DET produced behavioral effects at intramuscular doses of approximately 50 mg (0.65 to 0.85 mg/kg) (19). The duration of action of DET was somewhat longer (about 3 hr) than that of DMT. Interestingly, some subjects in the latter study reported, in contrast to Szara s findings, that DET produced a euphoric effect. Szara has suggested that this might be a dose-related phenomenon. 

In contrast, acute-duration exposure to up to 5,000 ppm -hexane for 20 hours a day for 5 consecutive days caused no changes in mouse sperm morphology when sperm were examined 5 weeks later (Mast et al. 1989a). Similar exposure also had no effect on the fertility of male mice over the following 8 weeks (Mastetal. 1989b). 

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