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Placebos Placebos are inactive substances, most often used in controlled studies for comparison with presumably active drugs. Effects: Placebos, although often considered inert and harmless, may have substantial effects—good and bad. They may help patients with many physical and mental disorders. But placebos may also produce nausea, headache, dizziness, sleepiness, insomnia, fatigue, depression, numbness, hallucinations, itching, vomiting, tremor, tachycardia, diarrhea, pallor, rashes, hives, ataxia, and edema. Some people have characteristics of drug addiction to a placebo: a tendency to increase the dose, a compulsive desire to take the substance, and an abstinence syndrome when they are deprived of it. All effects of placebos appear to be related to anticipation (usually, that the drug will work) or to spontaneous change. Spontaneous change, whether improvement, deterioration, or an entirely new problem (eg, headache, rash), may be mistakenly attributed to a placebo. Correlations between personality characteristics and response to placebos have not been well established. However, people who have dependent personalities and who want to please their physicians may be more likely to report beneficial effects; those with histrionic personalities may be more likely to report any effect, good or bad. Uses: In clinical studies comparing an active drug with a placebo, effects of placebo must be subtracted from those of the drug. The active drug must perform significantly better than the placebo to demonstrate efficacy. In some studies, placebo relieves the disorder in > 50% of patients, making demonstration of the active drug's efficacy difficult. A placebo may be used with the patient's consent to examine the patient's need for a potentially toxic drug—eg, to determine whether a patient with chronic pain is benefiting from a potentially addictive analgesic. However, obtaining consent is likely to undermine the placebo effect. The problem is solved by blindly alternating active drug and placebo. Rarely, when the prescriber determines that an active drug is not needed, placebos may be prescribed without a patient's knowledge to relieve symptoms or meet the patient's demands for treatment. Such use of a placebo may damage the physician-patient relationship and may make misinterpreting the patient's response more likely. If response to a placebo is positive, a physician may unjustifiably conclude that symptoms are not due to a physical disorder or that they are psychologically exaggerated. Thus, physicians are more likely to prescribe vitamins or vitamin B12 injections, which are often tantamount to placebos.
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