Tolerance continued stimulant

When use of the CNS stimulants causes insomnia, the nurse administers the drug early in the day (when possible) to diminish sleep disturbances. The patient is encouraged not to nap during the day. Other stimulants, such as coffee, tea, or cola drinks, are avoided. In some patients, nervousness, restlessness, and palpitations may occur. The vital signs are checked every 6 to 8 hours or more often if tachycardia, hypertension, or palpitations occur. Many times these adverse reactions will diminish with continued use as tolerance develops. If tolerance develops, the dosage is not increased. 

Despite the paucity of systematic studies in humans, the available evidence suggests that, like drugs such as alcohol, sedatives, and stimulants, inhalant drugs (i.e., solvents, general anesthetics, and nitrites) exert reinforcing effects and increase motor activity. Furthermore, with continuous use, these drugs appear to induce both tolerance and symptoms of withdrawal. 

In the meantime, there is continued interest in exploiting the use of induction ChT along with concurrent chemoradiation to maximize the opportunity to control occult micrometastases. There are potential downsides to this approach, as the induction ChT could reduce patient tolerance for the subsequent concurrent component. The induction ChT can also potentially stimulate accelerated tumor cell repopulation so that an additional burden of avidly dividing tumor is placed upon the subsequent concurrent chemoradiation. 

The psychomotor stimulants, cocaine and D-amphetamine, are considered together because they share a similar psychopharmacological profile.19 20 Low to moderate doses of both drugs given acutely to nontolerant, nonanxious subjects produce increases in positive mood (euphoria), energy, and alertness. Experienced cocaine users were unable to distinguish between intravenous (IV) cocaine and D-amphetamine,21 and cross-tolerance between cocaine and D-amphetamine with respect to their anorectic effect has been demonstrated.22 Additionally, the toxic psychosis observed after days or weeks of continued use of both psychostimulants is very similar. The fully developed toxic syndrome, characterized by vivid auditory and visual hallucinations, paranoid delusions, and... 

Chemical herbicides have been available for more than a century but major impacts on crop production awaited the development of "truely" selective herbicides or innovations that would permit use of non-selective herbicides in crop situations. We now have some form of selective chemical weed control for most of our major crops. However, continuing problems with herbicide injury to crops as well as poor control of weeds that are botanically similar to crops remind us that further improvements in herbicide selectivity are still needed. Introductions of new selective herbicides will continue but the high costs of these new chemicals are stimulating efforts to make wider use of existing herbicide chemistry. One successful approach has been to genetically improve the tolerance of new crop cultivars to major herbicides... 

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