دواء غفل

(تم التحويل من بلاسيبو)

الغفل أو (باللاتينية: placebo) هو عبارة عن مادة تأخذ شكل الدواء ولكنها لا تحتوي علي أية عناصر فعالة ولذلك فأن أي تغيير يحدث للمريض فإنه يرجع للعوامل النفسية فقط مثل الإيحاء والتوقع أو السير الطبيعي للمرض.

The placebo effect can be produced by inert tablets, by sham surgery, and by false information, such as when electrical stimulation is turned “off” in those with Parkinson’s disease implanted brain electrodes[1]
 
The placebo effect can be produced by inert tablets, by sham surgery, and by false information, such as when electrical stimulation is turned “off” in those with Parkinson’s disease implanted brain electrodes[1]
The placebo effect can be produced by inert tablets, by sham surgery, and by false information, such as when electrical stimulation is turned “off” in those with Parkinson’s disease implanted brain electrodes[1]

وقد اهتم علماء النفس بدراسة الأفراد الذين يؤثر عليهم الدواء الغفل وأشاروا أنهم أميل للاتصاف بالقلق النفسي أو الإنطواء.

ويستخدم الدواء الغفل أيضا في الدراسة التجريبية للأدوية؛ فمثلا يكون هناك مجموعتان من الأفراد المجموعة الأولى تتناول الدواء الحقيقي والمجموعة الثانية تتناول الدواء الغفل ولذك لمعرفة مدى التأثير الحقيقي لهذا الدواء على متناوليه. ,يستخدم الغفل في التجارب السريرية لتعمية الناس عن العلاج الذي يتلقونه، ولضمان التعمية الصحيحة، يجب أن يكون الغفل غير قابلاً للتمييز عن الدواء الفعّال، ففي التجارب السريرية الدوائية مثلاً، يجب أن تكون حبوب الغفل مطابقةً تماما لحبوب الدواء الفعال من حيث الشكل والحجم واللون والوزن. هذا ويستخدم الغفل أحياناً بشكل علاجي حيث يفيد نفسياً.

إن تأثير الغفل هو ظاهرة ممكن أن تؤدي لتخفيف أعراض المرض بوساطة علاج غير فعال، لمجرد أن المريض يريد أو يعتقد بأن هذا العلاج مفيد وفعال. ويعتبر مصطلح "تأثير الغفل" حديث فعلياً ويعبر عن التأثيرات المختلفة التي تجعل المرضى يعيدون التفكير بأعراض مرضهم.

حيث أن تأثير الغفل هو استجابة نفسية (سيكولوجية) للعلاج. والأمراض الجسدية لا تتحسن بتأثير الغفل. فالغفل لا يشفي المرض - كما يعتقد كثير من ا لناس - بل ما يحدث هو ملاحظة تحسن الأعراض والذي يميز تأثير الغفل.

ويجب أن يلاحظ أن جميع الأدوية تزيد من تأثير الغفل. وتعتبر المعالجات فعالة إن كان لها تأثير أقوى وأكثر فعالية من التأثيرات الناتجة عن الغفل.


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تعريفات

The American Society of Pain Management Nursing define a placebo as "any sham medication or procedure designed to be void of any known therapeutic value".[2]

In a clinical trial, a placebo response is the measured response of subjects to a placebo; the placebo effect is the difference between that response and no treatment.[3] It is also part of the recorded response to any active medical intervention.[4]

Any measurable placebo effect is termed either objective (e.g. lowered blood pressure) or subjective (e.g. a lowered perception of pain).[2]


التأثيرات

 
كيفيفة "عمل" العلاجات البديلة:
a) Misinterpreted natural course – the individual gets better without treatment.
b) Placebo effect or false treatment effect – an individual receives "alternative therapy" and is convinced it will help. The conviction makes them more likely to get better.
c) Nocebo effect – an individual is convinced that standard treatment will not work, and that alternative therapies will work. This decreases the likelihood standard treatment will work, while the placebo effect of the "alternative" remains.
d) No adverse effects – Standard treatment is replaced with "alternative" treatment, getting rid of adverse effects, but also of improvement.
e) Interference – Standard treatment is "complemented" with something that interferes with its effect. This can both cause worse effect, but also decreased (or even increased) side effects, which may be interpreted as "helping". Researchers, such as epidemiologists, clinical statisticians and pharmacologists, use clinical trials to reveal such effects, allowing physicians to offer a therapeutic solution best known to work. "Alternative treatments" often refuse to use trials or make it deliberately hard to do so.

Placebos can improve patient-reported outcomes such as pain and nausea.[5] This effect is unpredictable and hard to measure, even in the best conducted trials.[5] For example, if used to treat insomnia, placebos can cause patients to perceive that they are sleeping better, but do not improve objective measurements of sleep onset latency.[6] A 2001 Cochrane Collaboration meta-analysis of the placebo effect looked at trials in 40 different medical conditions, and concluded the only one where it had been shown to have a significant effect was for pain.[7]

By contrast, placebos do not appear to affect the actual diseases, or outcomes that are not dependent on a patient's perception.[5] One exception to the latter is Parkinson's disease, where recent research has linked placebo interventions to improved motor functions.[8][9][10]

Measuring the extent of the placebo effect is difficult due to confounding factors.[11] For example, a patient may feel better after taking a placebo due to regression to the mean (i.e. a natural recovery or change in symptoms).[12][13][14] It is harder still to tell the difference between the placebo effect and the effects of response bias, observer bias and other flaws in trial methodology, as a trial comparing placebo treatment and no treatment will not be a blinded experiment.[5][12] In their 2010 meta-analysis of the placebo effect, Asbjørn Hróbjartsson and Peter C. Gøtzsche argue that "even if there were no true effect of placebo, one would expect to record differences between placebo and no-treatment groups due to bias associated with lack of blinding."[5]

Hróbjartsson and Gøtzsche concluded that their study "did not find that placebo interventions have important clinical effects in general."[5] Jeremy Howick has argued that combining so many varied studies to produce a single average might obscure that "some placebos for some things could be quite effective."[15] To demonstrate this, he participated in a systematic review comparing active treatments and placebos using a similar method, which generated a clearly misleading conclusion that there is "no difference between treatment and placebo effects".[16][15]

العوامل المؤثرة على قوة تأثير الدواء الغفل

 
Louis Lasagna helped make placebo-controlled trials a standard practice in the U.S..[17] He also believed "warmth, sympathy, and understanding" had therapeutic benefits.[18]

A review published in JAMA Psychiatry found that, in trials of antipsychotic medications, the change in response to receiving a placebo had increased significantly between 1960 and 2013. The review's authors identified several factors that could be responsible for this change, including inflation of baseline scores and enrollment of fewer severely ill patients.[19] Another analysis published in Pain in 2015 found that placebo responses had increased considerably in neuropathic pain clinical trials conducted in the United States from 1990 to 2013. The researchers suggested that this may be because such trials have "increased in study size and length" during this time period.[20]

Children seem to have greater response than adults to placebos.[21]

Some studies have investigated the use of placebos where the patient is fully aware that the treatment is inert, known as an open-label placebo.[22] A meta-analysis found some evidence that open-label placebos may have positive effects in comparison to no treatment,[23] which may open new avenues for treatments,[22] but noted the trials were done with a small number of participants and hence should be interpreted with "caution" until further better controlled trials are conducted.[23][22]

الأعراض والأمراض

A 2010 Cochrane Collaboration review suggests that placebo effects are apparent only in subjective, continuous measures, and in the treatment of pain and related conditions.[5]

الأم

Placebos are believed to be capable of altering a person's perception of pain. "A person might reinterpret a sharp pain as uncomfortable tingling."[24]

One way in which the magnitude of placebo analgesia can be measured is by conducting "open/hidden" studies, in which some patients receive an analgesic and are informed that they will be receiving it (open), while others are administered the same drug without their knowledge (hidden). Such studies have found that analgesics are considerably more effective when the patient knows they are receiving them.[25]

الاكتئاب

In 2008, a controversial meta-analysis led by psychologist Irving Kirsch, analyzing data from the FDA, concluded that 82% of the response to antidepressants was accounted for by placebos.[26] However, there are serious doubts about the used methods and the interpretation of the results, especially the use of 0.5 as cut-off point for the effect-size.[27] A complete reanalysis and recalculation based on the same FDA data discovered that the Kirsch study suffered from "important flaws in the calculations". The authors concluded that although a large percentage of the placebo response was due to expectancy, this was not true for the active drug. Besides confirming drug effectiveness, they found that the drug effect was not related to depression severity.[28]

Another meta-analysis found that 79% of depressed patients receiving placebo remained well (for 12 weeks after an initial 6–8 weeks of successful therapy) compared to 93% of those receiving antidepressants. In the continuation phase however, patients on placebo relapsed significantly more often than patients on antidepressants.[29]

الآثار السلبية

A phenomenon opposite to the placebo effect has also been observed. When an inactive substance or treatment is administered to a recipient who has an expectation of it having a negative impact, this intervention is known as a nocebo (Latin nocebo = "I shall harm").[30] A nocebo effect occurs when the recipient of an inert substance reports a negative effect or a worsening of symptoms, with the outcome resulting not from the substance itself, but from negative expectations about the treatment.[31][32]

Another negative consequence is that placebos can cause side-effects associated with real treatment.[33] Failure to minimise nocebo side-effects in clinical trials and clinical practice raises a number of recently explored ethical issues. [34]

Withdrawal symptoms can also occur after placebo treatment. This was found, for example, after the discontinuation of the Women's Health Initiative study of hormone replacement therapy for menopause. Women had been on placebo for an average of 5.7 years. Moderate or severe withdrawal symptoms were reported by 4.8% of those on placebo compared to 21.3% of those on hormone replacement.[35]

الأخلاقيات

في التجارب البحثية

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في الممارسة الطبية

الآليات

Expectation plays a clear role. A placebo presented as a stimulant may trigger an effect on heart rhythm and blood pressure, but when administered as a depressant, the opposite effect.[36]

علم النفس

 
The "placebo effect" may be related to expectations

In psychology, the two main hypotheses of placebo effect are expectancy theory and classical conditioning.[37]

In 1985, Irving Kirsch hypothesized that placebo effects are produced by the self-fulfilling effects of response expectancies, in which the belief that one will feel different leads a person to actually feel different.[38] According to this theory, the belief that one has received an active treatment can produce the subjective changes thought to be produced by the real treatment. Similarly, the appearance of effect can result from classical conditioning, wherein a placebo and an actual stimulus are used simultaneously until the placebo is associated with the effect from the actual stimulus.[39] Both conditioning and expectations play a role in placebo effect,[37] and make different kinds of contribution. Conditioning has a longer-lasting effect,[40] and can affect earlier stages of information processing.[41] Those who think a treatment will work display a stronger placebo effect than those who do not, as evidenced by a study of acupuncture.[42]

Additionally, motivation may contribute to the placebo effect. The active goals of an individual changes their somatic experience by altering the detection and interpretation of expectation-congruent symptoms, and by changing the behavioral strategies a person pursues.[43] Motivation may link to the meaning through which people experience illness and treatment. Such meaning is derived from the culture in which they live and which informs them about the nature of illness and how it responds to treatment.

التسكين الوهمي

Functional imaging upon placebo analgesia suggests links to the activation, and increased functional correlation between this activation, in the anterior cingulate, prefrontal, orbitofrontal and insular cortices, nucleus accumbens, amygdala, the brainstem periaqueductal gray matter,[44][45] and the spinal cord.[46][47][48]

It has been known that placebo analgesia depends upon the release in the brain of endogenous opioids since 1978.[49] Such analgesic placebos activation changes processing lower down in the brain by enhancing the descending inhibition through the periaqueductal gray on spinal nociceptive reflexes, while the expectations of anti-analgesic nocebos acts in the opposite way to block this.[46]

Functional imaging upon placebo analgesia has been summarized as showing that the placebo response is "mediated by "top-down" processes dependent on frontal cortical areas that generate and maintain cognitive expectancies. Dopaminergic reward pathways may underlie these expectancies".[50] "Diseases lacking major 'top-down' or cortically based regulation may be less prone to placebo-related improvement".[51]

المخ والجسم

In conditioning, a neutral stimulus saccharin is paired in a drink with an agent that produces an unconditioned response. For example, that agent might be cyclophosphamide, which causes immunosuppression. After learning this pairing, the taste of saccharin by itself is able to cause immunosuppression, as a new conditioned response via neural top-down control.[52] Such conditioning has been found to affect a diverse variety of not just basic physiological processes in the immune system but ones such as serum iron levels, oxidative DNA damage levels, and insulin secretion. Recent reviews have argued that the placebo effect is due to top-down control by the brain for immunity[53] and pain.[54] Pacheco-López and colleagues have raised the possibility of "neocortical-sympathetic-immune axis providing neuroanatomical substrates that might explain the link between placebo/conditioned and placebo/expectation responses."[53]:441 There has also been research aiming to understand underlying neurobiological mechanisms of action in pain relief, immunosuppression, Parkinson's disease and depression.[55]

Dopaminergic pathways have been implicated in the placebo response in pain and depression.[56]

العوامل الخارجية

Placebo-controlled studies, as well as studies of the placebo effect itself, often fail to adequately identify confounding factors.[24][57][58] False impressions of placebo effects are caused by many factors including:[24][12][58][37][57]

  • Regression to the mean (natural recovery or fluctuation of symptoms)
  • Additional treatments
  • Response bias from subjects, including scaling bias, answers of politeness, experimental subordination, conditioned answers;
  • Reporting bias from experimenters, including misjudgment and irrelevant response variables.
  • Non-inert ingredients of the placebo medication having an unintended physical effect

التاريخ

 
A quack treating a patient with Perkins Patent Tractors by James Gillray, 1801. John Haygarth used this remedy to illustrate the power of the placebo effect.



انظر أيضاً


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