Drugs fortunate side effects

Caffeine is the most widely consumed stimulant drug in the world. It occurs naturally in coffee, tea, and the cola nut and is added to many soft drinks. Many of us consume coffee and soft drinks because of the desirable stimulatory effects produced by caffeine many of us have consumed too much caffeine and felt the consequences. The undesirable effects of caffeine, the agitation, the inability to concentrate, the mild tremors, and the general unpleasantness, are a form of neurotoxicity. Literally your brain, and more specifically, the adenosine receptors in your brain, has too much caffeine. These effects are a reversible form of neurotoxicity. Fortunately, we metabolize caffeine quickly and the undesirable effects end. By experience we have learned how to moderate our caffeine consumption to avoid the unpleasant side effects. A great deal of money is made from the neuroactive and physiological effects of caffeine. You can learn more about this fascinating drug in the chapter on caffeine. 

A long list of adverse effects may imply that most patients experience many of them to a significant degree. In fact, although almost all patients will experience some mild side effects with these drugs, such as dry mouth or tremor, they are usually transitory and disappear with time, medication reduction, or discontinuation. Fortunately, these effects are rarely serious or irreversible, and on average, the typical complications with antipsychotics are no worse than with medications prescribed for other medical disorders. 

Thus, virtually all side effects of the selective NRIs can be understood as undesirable actions of norepinephrine in undesirable pathways at undesirable receptor subtypes. Just as for the SSRls, this occurs because it is not possible for a systemically administered drug to act only at the desirable receptors in the desirable places it must act everywhere it is distributed, which means all over the brain and all over the body. Fortunately, selective NRI side effects are more of a nuisance than a danger, and they generally attenuate over time, although they can cause an important subset of p>atients to discontinue treatment. 

As might be expected, ganglionic blockers produce a multitude of side effects because of the inhibition of both sympathetic and parasympathetic responses. Some adverse effects include gastrointestinal discomfort (nausea, constipation), urinary retention, visual disturbances, and orthostatic hypotension. At higher doses, they may even exhibit some neuromuscular blocking activity. These and other side effects may be quite severe in some patients. Fortunately, ganglionic blockers are usually not used for extended periods because the patient is placed on other antihypertensive drugs when the hypertensive crisis is resolved. 

The most important adverse effects of efavirenz involve the CNS. Up to 53% of patients report some CNS or psychiatric side effects, but fewer than 5% discontinue the drug for this reason. CNS symptoms may occur with the first dose and may last for hours. More severe symptoms may require weeks to resolve. Patients commonly report dizziness, impaired concentration, dysphoria, vivid or disturbing dreams, and insomnia. Episodes of frank psychosis (depression, hallucinations, and/or mania) have been associated with initiating efavirenz. Fortunately, CNS side effects generally become more tolerable and resolve within the first 4 weeks of therapy. 

Most drugs produce more than one physiological response. In general, one response is the desired response, and the rest are considered to be undesirable side effects. However, in some cases, the side effects have turned out to be fortunate discoveries. These accidental discoveries have led to the development of novel treatments for a wide range of ailments. The following are some of the better-known historical examples of this phenomenon. 

---