The kinetics and dynamics of responses to placebo

Placebo: a brief updated review

Our aims were to provide updated information on placebo/nocebo effect and the potential use of placebo in clinical practice. This article can only provide a rough overview on the placebo and nocebo effect and is intended to serve as a starting point for the reader to go deeper into the corresponding literature. The placebo effect has been observed in multiple medical conditions, after oral administration, with manual therapies as well as with surgery and invasive procedures. The use of placebo in clinical trials is fundamental, although the ethics of its use is under discussion. The placebo may behave like a drug from the pharmacokinetic and pharmacodynamic point of view and can also be associated with adverse events (nocebo effect). Placebo can modify treatment by increasing or decreasing the effects of drugs. The factors associated with the occurrence of placebo effect are multiple, but in addition to those that depend on the placebo itself, the doctor-patient relationship would be the most important. As a result of findings that were published in the last two decades, the psycho-neurobiological basis of placebo is becoming better understood, although further studies are needed. In conclusion, the placebo effect in the clinic exhibits weak to moderate intensity. Placebo, in addition to its use in the clinical trial, should be considered another therapeutic remedy either as stand alone or in association with treatment, and could be useful in certain circumstances. The use of placebo should be regulated by the European health authorities through a guide in clinical practice that will improve patient care.

The Powerful Placebo Effect in Cough: Relevance to Treatment and Clinical Trials

Interest in the placebo effect of medicines has developed from the use of placebo treatments as controls in clinical trials into a whole new area of research around how placebos fit into a psychosocial model of therapeutics. The large placebo effect associated with cough medicines is both a problem and an opportunity for researchers: a problem for clinical trials on new actives as the active must beat the large placebo effect, and an opportunity for harnessing the placebo effect to produce effective cough medicines without any pharmacologically active ingredient. This review discusses the mechanisms associated with the placebo effect of cough medicines and distinguishes between a 'perceived placebo effect' and a true 'placebo effect'. The efficacy of sweeteners in cough syrups is discussed as well as viscosity, mucoadhesion, and flavoring. The complexity of modern cough medicines is demonstrated by an example of a medicine which contains one active ingredient, and eighteen excipients which provide a complex and intense sensory experience to enhance the placebo effect and complement the pharmacological activity of the medicine.

Analgesic efficacy of parenteral paracetamol (propacetamol) and diclofenac in post-operative orthopaedic pain

BACKGROUND

Propacetamol is an injectable pro-drug of paracetamol (acetaminophen) with analgesic and antipyretic activities, especially used in the post-operative period. The aim of this study was to assess the analgesic efficacy and safety of intravenous paracetamol, administered as propacetamol, in comparison with placebo and intramuscular diclofenac in patients with post-operative pain.

METHODS

This was a randomized, double-blind, double-dummy study. One hundred and twenty patients with moderate to severe pain following total hip arthroplasty received either two administrations of propacetamol 2 g intravenously, 5 h apart (n = 40), one single administration of diclofenac 75 mg intramuscularly (n = 40) or placebo (n = 40). Efficacy measures were assessed before each drug administration, for the 5 h following each study treatment administration and for the total study duration of 10 h. Safety was assessed by reporting adverse events and changes in vital signs, electrocardiogram (ECG) and biochemical investigations before and 24 h after dosing.

RESULTS

Both active treatments were effective and statistically superior to placebo over the whole study period, as indicated by the total pain relief score. No significant differences were found between propacetamol and diclofenac for any measures of analgesic activity. Only minor and common adverse events were reported, with no overall differences between the groups.

CONCLUSION

Both active treatments were superior to placebo, and the overall efficacy of two intravenous infusions of propacetamol 2 g (equivalent to 1 g of paracetamol), 5 h apart, was not statistically different from that provided by a single intramuscular injection of diclofenac 75 mg over the first 5 h post-dose and over the total 10-h study period. The safety was good.

Estrogen raises the sweating threshold in postmenopausal women with hot flashes

OBJECTIVE

To determine if estrogen ameliorates hot flashes by raising the core body temperature sweating threshold, by reducing core body temperature fluctuations, and/or by reducing sympathetic activation (as measured by plasma 3-methoxy-4-hydroxyphenylglycol).

DESIGN

Laboratory physiological study.

SETTING

University medical center.

PATIENT(S)

Twenty-four healthy postmenopausal women reporting frequent hot flashes.

INTERVENTION(S)

Participants were randomly assigned, in double-blind fashion, to receive 1 mg/d 17beta-estradiol orally or placebo for 90 days.

MAIN OUTCOME MEASURE(S)

Core body temperature, core body temperature fluctuations, mean skin temperature, sternal sweat rate, laboratory hot flash counts (sternal skin conductance), plasma 3-methoxy-4-hydroxyphenylglycol.

RESULT(S)

The E(2) group had significant increases in plasma E(2) (8 +/- 2 vs. 132 +/- 22 pg/mL) and core body temperature sweating threshold (37.98 +/- 0.09 vs. 38.14 +/- 0.09 degrees C) and decreases in plasma FSH (58.8 +/- 8.9 vs. 40.1 +/- 7.6 mIU/mL) and hot flashes (1.4 +/- 0.5 vs. 0.6 +/- 0.6). These changes did not occur in the placebo group. There were no significant changes in any other measure.

CONCLUSION(S)

E(2) ameliorates hot flashes by raising the core body temperature sweating threshold, but does not affect core temperature fluctuations or plasma 3-methoxy-4-hydroxyphenylglycol.

Placebos, placebo effect, and the response to the healing situation: the evolution of a concept

In spite of its impressive progress, medicine has been strongly criticized for relying on its modern biomedical tradition to the neglect of the psychosocial aspects of health. This neglect may account for patients' dissatisfaction and eventual use of alternative health approaches. The concept of placebo has sustained dramatic "protean" metamorphoses through the ages. For centuries, placebos have been regarded as powerful deceptive therapies. From the middle of the twentieth century, however, conventional medicine has used placebos as methodologic tools to distinguish the specific from the nonspecific ingredients in treatments. In modern medical research, the double-blind, placebo-controlled, randomized clinical trial has been established as the gold standard for the assessment of any new treatment. Recently a new trend regarding placebos seems to have emerged. The placebo and other nonspecific effects elicited by the "healing situation" have been independently subjected to scientific study. Progress in this area may promote useful clinical applications, enabling physicians to broaden their perspectives on the healing process. We present the historical changes of the concept of placebo and the ethical issues raised by their use.

Culture and psychopharmacology

In this brief review the authors strive to provide a broad overview of various factors that impinge on psychopharmacotherapeutic practices. The literature revealed an impressive progress in research focusing on the delineation of the biologic mechanisms responsible for cross-ethnic variations in psychotropic metabolism and effects. With the field progressing at an accelerating pace, there is little doubt that in the coming decade clinicians will be provided with a detailed map showing the prevalence and distribution of genetic polymorphisms of most, if not all, of the drug-metabolizing enzymes, and clinicians also will have an overall picture on what these polymorphisms mean clinically. At the same time, clinicians should also start to have a good grasp on the meaning of the variations of the genes that encode therapeutic targets of psychotropics (e.g., neurotransmitter transporters and receptors). Such genetic fingerprinting, which will soon become a clinical reality, will provide tremendous help in ensuring that pharmacotherapies are increasingly more individually tailored, taking into consideration each patients genetic makeups that vary substantially across ethnic groups. As exciting as these new developments will be, they are dwarfed by the challenges ahead on the cultural side of the equation. Issues that are still awaiting further clarification include the following: How do we assess patients' beliefs and expectations related to psychotropic treatment? How do we minimize the communication gaps between patients and clinicians who are often from divergent sociocultural backgrounds? To what extent, and in what ways, do cultural (environmental) factors interact with biologic factors, and what might be the most efficient way to systematically assess such interactions? Data that have emerged in the past several decades clearly indicate the importance of culture and ethnicity in influencing patients' psychopharmacological response. It is expected that continuing progress in the near future will bring a better understanding on the way these cultural and biologic processes, separately and in interaction with each other, mediate treatment responses. Such knowledge will be crucial for the optimal pharmacotherapeutic care of for the majority of patients who will increasingly be of diverse ethnic and cultural backgrounds and will represent a significant contribution to the field of psychopharmacology as a whole.

The placebo response to citric acid-induced cough: pharmacodynamics and gender differences

Characteristics of the response to placebo in a citric acid-induced cough challenge were investigated as part of a randomized, double-blind crossover trial to assess the antitussive effect of dextromethorphan. Baseline cough responses were established on two occasions in 22 healthy subjects. They received 60 ml placebo antitussive syrup and cough frequency following five inhalations of 10% citric acid over 5 min was measured at regular intervals up to 12 h. Response-time models of varying complexity were used to describe the placebo cough suppression data. The cough response to placebo was also compared to that of the untreated state. The placebo cough response was best characterized by a non-linear increase in cough suppression up to a maximum reduction of 1.6 coughs from baseline at 4-4.5 h, followed by a non-linear return to baseline. The cough response in the untreated state was not different from that of placebo (P=0.99). Females coughed more frequently than males (median number of coughs=10.5 vs. 9.0, respectively P<0.001; Mann-Whitney U test), and adaptation to the cough stimulus was significantly more rapid in females (P<0.025). Accordingly, in trials that use citric acid-induced cough, gender should be considered in study design, particularly in relation to the timing of measurements.

The placebo effect

Placebos have been traditionally regarded as deceptive therapies and have not been understood in the broader context of social symbols and of interpersonal factors that surround the healing process itself. Although the power of inert substances to heal is well recognized, the placebo effect also influences the outcome of conventional therapies. The role of the placebo in modern medicine is poorly defined because of a lack of a common understanding of what the placebo effect is and because of the negative connotions associated with its use. The response rate to placebo varies by illness. The natural course of disease and patient or physician bias can be misinterpreted as a placebo response. In research, the placebo effect is therapeutic noise to be removed by placebo-controlled trials. Few studies are designed to measure the placebo response rate directly. Placebos are a reminder of how little is known about mind-body interaction. The placebo effect may be one of the most versatile and underused therapeutic tools at the disposal of physicians.

Are randomized control trial outcomes influenced by the inclusion of a placebo group?: a systematic review of nonsteroidal antiinflammatory drug trials for arthritis treatment

Placebo groups are often included in randomized control trials evaluating drug therapy, yet we know little about the placebo effect. The purpose of our study was to evaluate how the presence of a placebo group in a randomized control trial (RCT) influences the patients' ratings of the efficacy of an active drug therapy and their reporting of its adverse effects. We identified studies published between 1966 and 1994 using MEDLINE. Randomized control trials evaluating acetylsalicylic acid, diclofenac, or indomethacin for the treatment of osteo or rheumatoid arthritis were included in our sample. Two investigators independently extracted data. Fifty-eight treatment arms met our inclusion criteria and were available for analysis. Twenty-five treatment arms evaluated a nonsteroidal antiinflammatory drug (NSAID) in placebo control trials and 33 in comparative trials. Using a logistic regression model to adjust for the differences between the evaluated drugs and between the types of arthritis, we found that patients receiving an NSAID in a placebo control trial were more likely to withdraw due to inefficacy (OR=1.3; 95% CI, 1.0 to 1.6; P=0.04). Using a similar model, withdrawals due to adverse effects were found to be more common when the NSAID was given in trials that did not include a placebo group (OR=1.5; 95% CI, 1.1 to 1.9; P=0.002) as were reports of cutaneous (OR=4.2; 95% CI, 1.7 to 9.9), gastrointestinal (OR=1.6; 95% CI, 1.3 to 2.0), and other types (OR=5.3; 95% CI, 3.8 to 7.4) of adverse effects. Although reports of central nervous system adverse effects were more frequent in the comparative trials, this difference was not significant. Including a placebo group in a RCT changes how patients rate the efficacy and adverse effects of their therapy. Our results highlight the need to consider the placebo effect in the design and analyses of clinical trials.