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A double-blind, randomized, placebo-controlled trial of augmentation with lamotrigine or placebo in patients concomitantly treated with fluoxetine for resistant major depressive episodes.

BACKGROUND: Evidence of the antidepressant efficacy of lamotrigine is increasing, although there are no placebo-controlled trials of lamotrigine augmentation in depression. The aim of this study was to assess if augmentation with lamotrigine was superior to placebo in patients who were receiving fluoxetine for resistant major depressive episodes. METHOD: Twenty-three patients who had experienced at least 1 major depressive episode that was resistant to at least 1 prior trial of antidepressant therapy were selected. These patients were treated with fluoxetine, 20 mg/day, and concomitantly randomly assigned to receive either lamotrigine (N = 13) or placebo (N = 10) for 6 weeks. The dose of lamotrigine was titrated upward from 25 mg/day to 100 mg/day. Patients suffering from bipolar II disorder (N = 8) or from major depressive disorder (N = 15) (DSM-IV criteria) were enrolled, resulting in heterogeneity of the sample. The primary outcome measure was Hamilton Rating Scale for Depression score. Data were collected from 2000-2001. RESULTS: Lamotrigine was statistically superior to placebo on the Clinical Global Impressions scale at endpoint, both in absolute terms (mean +/- SD Clinical Global Impressions-Severity of Illness scores: lamotrigine, 2.15 +/- 1.28; placebo, 3.40 +/- 1.17; p =.0308) and using a responder analysis, with response defined as a Clinical Global Impressions-Improvement score of 2 or less (lamotrigine, 84.62% [N = 11]; placebo, 30.00% [N = 3]; p =.013). The effect of lamotrigine on Clinical Global Impressions scale scores was seen in both major depressive disorder and bipolar II disorder. Lamotrigine, however, failed to separate statistically from placebo on the Hamilton Rating Scale for Depression and Montgomery-Asberg Depression Rating Scale. This failure to differentiate on a primary outcome measure is essentially a negative study result. This result is most likely an artifact of the small sample size used and the resultant limited power of the study. CONCLUSION: The results of this trial add to the literature suggesting potential efficacy of the antidepressant profile of lamotrigine. In addition, this study points to a possible role of lamotrigine as an augmentation agent in depression.

Adolescent↗

Responders, nonresponders, and placebo responders among children with attention deficit disorder. Importance of a blinded placebo evaluation.

The responses to methylphenidate of 118 children with attention deficit disorder (ADD) were studied under double-blind conditions. Three distinct types of response to medication and placebo were found, as determined by teacher ratings. One group, called "responders," improved dramatically in attention and hyperactivity ratings on active medication but showed essentially no change from baseline when on placebo. The group called "nonresponders" showed minimal change in ratings on either placebo or medication. The third group, "placebo responders," showed almost as much improvement as the responders on medication, but their ratings were not very different from medication ratings during the placebo trial. The placebo responders, 18 percent of the group, would have been considered responders in a nonplacebo-controlled study. Double-blind placebo evaluation of ADD children can and should be done by practitioners to avoid medicating children who are responding to nonspecific effects of drugs.

Analysis of Variance↗

Evaluation by 24-hour ambulatory blood pressure monitoring of efficacy of manidipine hydrochloride 10, 20 or 40 mg once daily as compared to placebo in treating mild to moderate essential hypertension: a double-blind, randomized, parallel group, placebo-controlled study.

In a double-blind, randomized, placebo-controlled, parallel-group study the ambulatory blood pressure monitoring (ABPM) and relative tolerability of different doses of manidipine hydrochloride (10, 20 and 40 mg) were compared to placebo in patients with mild to moderate essential hypertension. After an initial 2-week run-in period on placebo, 52 patients, 32 males and 20 females, aged 40 to 63 years, were randomized to receive manidipine 10 mg, 20 mg, 40 mg or placebo, all administered once daily for 4 weeks. Patients were checked after the initial placebo phase and every 2 weeks thereafter. At each visit, casual BP and HR were measured. At the end of the placebo period and after 4 weeks of active treatment, non-invasive 24-h ABPM was performed. 24-h, day-time and night-time ambulatory BP as well as the area under the curve (AUC) and casual BP were dose-dependently reduced by manidipine 10, 20 and 40 mg, without changes in the normal BP circadian profile. The trough:peak ratio for both SBP and DBP was higher than 50% for all three manidipine dosage regimens. The percentage of abnormal ambulatory SBP and DBP readings was significantly reduced in all manidipine-treated groups versus placebo. The risk/benefit ratio suggests that the intermediate manidipine dosage (20 mg) could be a suitable dose regimen for the majority of patients with mild to moderate hypertension.

Adult↗

A comparison of drugs versus placebo for the treatment of dysthymia.

OBJECTIVES: Dysthymia is a depressive disorder of chronic nature but of less severity than major depression, which depressive symptoms are more or less continuous for at least two years. The aim of this review was to conduct a systematic review of all RCTs comparing drugs and placebo for dysthymia. SEARCH STRATEGY: Electronic searches of Cochrane Library, EMBASE, MEDLINE, PsycLIT, Biological Abstracts and LILACS; reference searching; personal communication; conference abstracts; unpublished trials from the pharmaceutical industry; book chapters on the treatment of depression. SELECTION CRITERIA: The inclusion criteria for all randomised controlled trials were that they should focus on the use of drugs versus placebo for dysthymic patients. Exclusion criteria were: non randomised, mixed major depression/ dysthymia (trials not providing separate data) and depression secondary to other disorders (e.g. substance abuse). DATA COLLECTION AND ANALYSIS: The reviewers extracted the data independently. In order to achieve an intention-to-treat analysis, when trials failed to report it was assumed that people who died or dropped out had no improvement. Authors of relevant trials were contacted for additional and missing data. Absence of treatment response as defined by authors was the main measure of outcome used. Relative Risks (RR) and 95% confidence intervals (CI) of dichotomous data were calculated with the Random Effects Model. Where possible, number needed to treat (NNT) and number needed to harm (NNH) were estimated, taking the reciprocal of the absolute risk reduction. MAIN RESULTS: Currently the review includes 15 trials. Similar results were obtained in terms of efficacy for different groups of drugs, such as tricyclic (TCA), selective serotonin reuptake inhibitors (SSRI), monoamine oxidase inhibitors (MAOI) and other drugs (sulpiride, amineptine, and ritanserin). The pooled RR for absence of treatment response was 0. 68 (95% CI 0.59-0.78) for TCA and the NNT was 4.3 (95% CI 3.2-6.5). SSRIs showed similar RR for this outcome: 0.64 (95% CI 0.55-0.74), the NNT being 4.7 (95% CI 3.5-6.9). Concerning MAOIs, the RR was 0. 59 (95% CI 0.48-0.71) and the NNT was 2.9 (95% CI 2.2-4.3). Other drugs (amisulpride, amineptine and ritanserin) showed similar results in terms of absence of treatment response. Using more stringent criteria for improvement - full remission - the results were unchanged. Patients treated on TCA were more likely to report adverse events, compared with placebo. REVIEWER'S CONCLUSIONS: Drugs are effective in the treatment of dysthymia with no differences between and within class of drugs. Tricyclic antidepressants are more likely to cause adverse events and dropouts. As dysthymia is a chronic condition, there remains little information on quality of life and medium or long-term outcome.

Antidepressive Agents↗

The ethics of placebo-controlled trials: a comparison of inert and active placebo controls.

Because of the recent and controversial example of sham surgery for the evaluation of fetal tissue transplants for Parkinson's disease, there is renewed interest in the ethics of using "active" placebos in surgical trials, where otherwise there are no inert procedures available, and in pharmacological trials, where there are inert substances, but where patients may guess to which arm they have been allocated. This paper seeks to clarify the ethical arguments surrounding the use of active placebos in trials, and to set up a notation for assessing the ethics of trials more generally. We first establish an framework by which ethics committees can analyze such trials. We examine (1) the scientific value of the research; (2) the expected risks and benefits to individual patients, and (3) the voluntary nature of consent. We then contrast the implications of this framework for inert and active placebo-controlled trials, respectively. In particular, we analyze their relative expected utility using three main utility factors, namely, treatment effects, placebo effects, and altruism. We conclude that, when the intervention is already widely available, active placebo trials rely more heavily on altruism than do inert placebo trials and, when the intervention is restricted, this excess reliance may not be needed. What our analysis provides is the explicit justification for the apparent caution of Institutional Review Boards or ethics committees when reviewing sham operations, especially when the expected harm is not trivial and the risk of exploitation is high.

Clinical Trials as Topic↗

Aspartame is no more likely than placebo to cause urticaria/angioedema: results of a multicenter, randomized, double-blind, placebo-controlled, crossover study.

BACKGROUND: Anecdotes and single case reports have suggested that the high-intensity sweetener, aspartame, may be associated with allergic/hypersensitivity-type reactions. METHODS: We conducted a multicenter, placebo-controlled clinical study to evaluate individuals who had experienced urticaria and/or angioedema allegedly associated with ingestion of an aspartame-containing product. Despite extensive recruiting efforts over 4 years, only 21 subjects could be enrolled. After admission to clinical research units, subjects were given aspartame and placebo in a randomized, double-blind, crossover fashion. Subjects received, on different days, increasing doses (50, 300, 600 mg) of aspartame and placebo at 8:00 AM, 10:00 AM, and noon. Subjects who weighed less than 40 kg received one half of these doses. Conversion products of aspartame, aspartyl-phenylalanine diketopiperazine and beta-aspartame, were also included in the aspartame arm of the study. Positive reactions were defined as urticaria (hives with wheals 4 mm or more in diameter with a collective diameter of at least 15 mm or one or more hives with a wheal of 4 mm or greater with a flare of 8 mm or greater) or as angioedema. RESULTS: According to these criteria, four reactions were observed; two followed aspartame ingestion and two followed placebo ingestion (p = 1.00). The incidence of other adverse experiences was no different after aspartame versus placebo ingestion (p = 0.289). CONCLUSION: These results indicate that aspartame and its conversion products are no more likely than placebo to cause urticaria and/or angioedema reactions in subjects with a history consistent with hypersensitivity to aspartame.

Administration, Oral↗

Placebos: a review of the placebo response.

Placebos have been a component of healing since the beginning. Whether consciously or unconsciously given, they are largely responsible for the success of medicine before randomized trials. Yet, even in this era of "evidence-based medicine," placebos remain enigmatic, and elicit mixed attitudes from divers disciplines. However, our ignorance is not total. There are a few facts to cling to and old myths to dispel. The effect of placebos seems to encompass such disparate elements as anxiety, conditioning, expectation, the healer's persona, and the attachment of meaning to illness. Placebos may obscure as well as illuminate the truth about treatment effectiveness. Moreover, it is easy to confuse their effect with the natural progression of the disease being treated. Those engaged in treatment trials must recognize and manage the reality of placebos rather than attempt to eliminate or disparage them. Factors that might influence the placebo effect such as age, gender, and social circumstances need prospective study. Meanwhile doctors, through honest and compassionate interactions with patients, should strive to maximize their treatments' benefits. This implies confident reassurance and the provision of some meaning to the person's symptoms.

Anxiety↗

Multicenter, placebo-controlled trial comparing acarbose (BAY g 5421) with placebo, tolbutamide, and tolbutamide-plus-acarbose in non-insulin-dependent diabetes mellitus.

BACKGROUND: Acarbose delays release of glucose from complex carbohydrates and disaccharides by inhibiting intestinal alpha-glucosidases, thereby attenuating postprandial increments in blood glucose and insulin. This multicenter, double-blind, placebo-controlled study compared the efficacy and safety of diet alone, acarbose, tolbutamide, and acarbose-plus-tolbutamide in non-insulin-dependent diabetes mellitus (NIDDM) patients. PATIENTS AND METHODS: A total of 290 patients with NIDDM and fasting plasma glucose levels of at least 140 mg/dL were randomized to receive treatment TID with acarbose 200 mg, tolbutamide 250 to 1,000 mg, a combination of both drugs, or placebo. A 6-week run-in period was followed by double-blind treatment for 24 weeks, then a 6-week follow-up period. RESULTS: All active treatments were superior (P < 0.05) to placebo in reducing postprandial hyperglycemia and HbA1c levels. The ranking in order of efficacy was: acarbose-plus-tolbutamide, tolbutamide, acarbose, and placebo. The postprandial reductions in glucose were approximately 85 mg/dL for acarbose-plus-tolbutamide, 71 mg/dL for tolbutamide, 56 mg/dL for acarbose, and 13 mg/dL for placebo. Tolbutamide was associated with increases in body weight and postprandial insulin levels when taken alone, but these were ameliorated when tolbutamide was taken in combination with acarbose. Acarbose alone or in combination with tolbutamide caused significantly more gastrointestinal adverse events (mainly flatulence and soft stools or diarrhea) than tolbutamide or placebo, but these were generally well tolerated. Clinically significant elevations in hepatic transaminase levels occurred in 3 patients in the acarbose group and 2 in the acarbose-plus-tolbutamide group. Transaminase levels returned to normal when therapy was discontinued. CONCLUSIONS: Acarbose was effective and well tolerated in the treatment of NIDDM. Control of glycemia was significantly better with acarbose compared with diet alone. Acarbose-plus-tolbutamide was superior to tolbutamide alone.

Acarbose↗

Acupuncture compared to placebo-acupuncture for postoperative nausea and vomiting prophylaxis: a randomised placebo-controlled patient and observer blind trial.

This randomised, placebo-controlled, patient and observer blinded trial was conducted to determine whether acupuncture at the acupuncture point P6 is effective in preventing postoperative nausea and vomiting (PONV) compared to placebo acupuncture. Female patients (n = 220) scheduled for gynaecological or breast surgery were randomly assigned to two groups receiving either acupuncture (n = 109) or placebo acupuncture (n = 111). Each group was stratified for type of surgery and included two subgroups receiving intervention either before or after induction of anaesthesia. The incidence of PONV and/or antiemetic rescue medication within 24 h after surgery was the main outcome measure which showed no statistically significant difference between groups (43.7% acupuncture, 50.9% placebo, p = 0.27). The differences were more pronounced for patients having gynaecological surgery (48.9% acupuncture, 67.6% placebo, p = 0.07) than for those having breast surgery (38.7% acupuncture, 40.3% placebo, p = 0.86). The secondary outcome, vomiting, was significantly reduced by acupuncture from 39.6% to 24.8% (p = 0.03). Subgroup analysis showed no difference between applications of acupuncture before compared to after induction of anaesthesia.

Acupuncture Therapy↗

Patient Preference for Placebo, Acetaminophen (paracetamol) or Celecoxib Efficacy Studies (PACES): two randomised, double blind, placebo controlled, crossover clinical trials in patients with knee or hip osteoarthritis.

BACKGROUND: Acetaminophen (paracetamol) is recommended as the initial pharmacological treatment for knee or hip osteoarthritis. However, survey and clinical trial data indicate greater efficacy for non-steroidal anti-inflammatory drugs and cyclo-oxygenase-2 specific inhibitors. DESIGN: Two randomised, double blind, placebo controlled, crossover multicentre clinical trials, Patient Preference for Placebo, Acetaminophen or Celecoxib Efficacy Studies (PACES). PATIENTS: Osteoarthritis of knee or hip. INTERVENTION: "Wash out" of treatment; randomisation; 6 weeks of celecoxib 200 mg/day, acetaminophen 1000 mg four times a day, or placebo; second "wash out;" crossover to 6 weeks of second treatment. MEASUREMENTS: Western Ontario McMaster Osteoarthritis Index (WOMAC), visual analogue pain scale, patient preference between two treatments. RESULTS: Celecoxib was more efficacious than acetaminophen in both periods in both studies; WOMAC and pain scale scores differed at p<0.05 in period II and both periods combined of PACES-a and in periods I and II and both periods combined in PACES-b, but not in period I of PACES-a. Acetaminophen was more efficacious than placebo, generally p<0.05 in PACES-b, and >0.05 in PACES-a. Patient preferences were 53% celecoxib v 24% acetaminophen in PACES-a (p<0.001) and 50% v 32% in PACES-b (p = 0.009); 37% acetaminophen v 28% placebo in PACES-a (p = 0.340) and 48% v 24% in PACES-b (p = 0.007). No clinically or statistically significant differences were seen in adverse events or tolerability among the three treatment groups. CONCLUSIONS: Greater efficacy was seen for celecoxib v acetaminophen v placebo, while adverse events and tolerability were similar. Variation in results and statistical significance in the two different trials are of interest.

Acetaminophen↗

Zoledronic acid significantly reduces skeletal complications compared with placebo in Japanese women with bone metastases from breast cancer: a randomized, placebo-controlled trial.

PURPOSE: To investigate the efficacy and safety of zoledronic acid for the treatment of bone metastases from breast cancer. PATIENTS AND METHODS: Women with bone metastases (N = 228) were randomly assigned to receive 4 mg zoledronic acid (n = 114) or placebo (n = 114) via 15-minute infusions every 4 weeks for 1 year. The primary efficacy end point was the skeletal-related event (SRE) rate ratio between treatment groups. An SRE was defined as pathologic fracture, spinal cord compression, and radiation or surgery to bone. Secondary end points included percentage of patients with at least one SRE, time-to-first SRE, and Andersen-Gill multiple-event analysis. RESULTS: The SRE rate ratio at 1 year (excluding HCM and adjusted for prior fracture) was 0.61 (permutation test; P = .027), indicating that zoledronic acid reduced the rate of SRE by 39% compared with placebo. The percentage of patients with at least one SRE (excluding HCM) was significantly reduced by 20% by zoledronic acid (29.8% v 49.6% for placebo; P = .003). Zoledronic acid significantly delayed time-to-first SRE (median not reached v 364 days; Cox regression; P = .007) and reduced the risk of SREs by 41% in multiple event analysis (risk ratio = 0.59; P = .019) compared with placebo. Zoledronic acid was well tolerated with a safety profile similar to placebo. No patient treated with zoledronic acid had grade 3 or 4 serum creatinine increase. CONCLUSION: Zoledronic acid significantly reduced skeletal complications compared with placebo across multiple end points in Japanese women with bone metastases from breast cancer.

Adult↗

Reconsidering the role of personality in placebo effects: dispositional optimism, situational expectations, and the placebo response.

OBJECTIVE: Prior investigations have failed to find reliable personality differences in placebo responding. The present study tests the hypothesis that personality and situational variables interact to determine placebo responding. METHODS: Optimists and pessimists were randomly assigned to one of three conditions. In the first condition, the participants were told that they were to ingest a pill that would make them feel unpleasant (deceptive-expectation group). In the second condition, the participants were told that they were to ingest a pill that would make them feel either unpleasant or was an inactive substance (conditional-expectation group). Finally, a third group was told they were to ingest a pill that was inactive (control group). RESULTS: Pessimists were more likely than optimists to follow a negative-placebo expectation when given a deceptive expectation, but not when given a conditional expectation. CONCLUSION: The personality variable optimism-pessimism relates to placebo responding when individuals are given a deceptive but not a conditional expectation. This suggests that personality and situational variables interact to determine placebo responding.

Adult↗

Are more antiemetic trials with a placebo necessary? Report of patient data from randomized trials of placebo antiemetics with cisplatin.

BACKGROUND: Because of the predictability of significant emesis after its use, cisplatin serves as the standard emetic stimulus for trials of antiemetic drugs. To define better the incidence, severity, and pattern of emesis that follows cisplatin, facilitate the testing of new agents, and obviate the need for further placebo-controlled trials for this indication, individual patient data were compiled from completed studies with placebo antiemetics and cisplatin. METHODS: The time and number of emetic episodes during the 24 hours after cisplatin were obtained for 48 patients given a placebo antiemetic. Each was treated as part of a randomized, double-blind trial reported between 1981 and 1990. Emesis after antiemetic "rescue" therapy was also assessed. RESULTS: Emesis occurred in 47 of 48 patients (98% observed rate, 95% confidence interval, 89-99%). The median number of emetic episodes during the 24 hours after cisplatin was 6. Emesis continued after rescue in 77% of patients. CONCLUSIONS: Cisplatin caused severe emesis that persisted despite rescue in placebo-treated patients. Using the data presented, any therapy preventing acute emesis in 8 or more of the 48 individuals receiving cisplatin > 50 mg/m2 was an active antiemetic (P = 0.05). The four trials discussed here documented the antiemetic effectiveness of granisetron, metoclopramide, and ondansetron. The placebo-treated patients studied can serve as a control group for testing new therapies. Because of the certainty of severe emesis after cisplatin, and the availability both of these data and several proven drugs for this condition, prospective comparisons of antiemetics should employ active control medications.

Adult↗

Placebo response, placebo effect, and two attributes.

Two putative predictors of placebo response were studied in three samples of psychiatric outpatients. Two groups, 73 university medical center patients and 56 college health service patients, underwent 1 week of placebo treatment. A quasi-control group of 112 patients receiving no medication waited about 1 week before beginning psychotherapy. One attribute, acquiescence or traditionalism, predicted placebo response, thereby replicating prior findings. Acquiescence was unrelated to change in controls indicating that it may represent a correlate of true placebo effect under some conditions. Additional findings suggested qualifications as to the generality of the relationship. The second attribute, autonomic awareness, was associated with change in all three samples. It appeared to predict nonspecific improvement unrelated to placebo probably due to its relationship to intensity of somatization.

Adult↗

[On circadian variations of the placebo effect on the pain threshold of healthy teeth: Contribution to a physiology of placebo effects (author's transl)].

Placebo doses can influence the pain threshold of healthy teeth according to the label. Systematic longitudinal researches over the day with measuring the utilization time of cold stimulus on healthy front teeth demonstrate that the placebo effect is subject to significant circadian variations. During daytime a pseudo-analgesic causes a stronger and steeper onset of increase of the tooth pain threshold than during the night, when the pain threshold is influenced only minimal or even inverse. The placebo effect can come up to 40% of the pain threshold increase caused by a usual analgesic; this portion, however, is as well subject to high circadian variations. The extent of the placebo effect corresponds to the order of magnitude of the spontaneous circadian variations of pain threshold and correlates positively to it. These correlations are considered as indicating that those vegetative mechanisms causing the circadian variations of the pain threshold are equally involved in affecting the placebo actions.

Circadian Rhythm↗

A double-blind, placebo-controlled study of the safety and efficacy of ipratropium bromide nasal spray versus placebo in patients with the common cold.

Ipratropium bromide (IB) has been found to reduce secretions in the upper respiratory tract; this is accomplished through competitive inhibition of acetylcholine at muscarinic receptors that control rhinorrhea production. This study compared the safety and efficacy of IB with placebo in the symptomatic relief of rhinorrhea in patients with the common cold. Human subjects with symptoms of a common cold, primarily rhinorrhea, were enrolled and treated with either IB (84 micrograms/nostril) or placebo; each was administered as two sprays per nostril, four times a day, for 4 days. Primary efficacy analyses were in-clinic measurements of nasal discharge weights over a 3-hour period after administration on days 1 and 2 and assessment of rhinorrhea symptoms by use of a subjective patient-completed visual analog rating scale. IB significantly reduced rhinorrhea an average of 18% over placebo for days 1 and 2 (p = 0.01). Visual analog scale scores showed an average improvement in rhinorrhea of 22% over placebo (p = 0.001). When patients with relatively minor rhinorrhea (baseline weight of nasal discharge < or = 1.0 gm) were excluded, IB produced an average reduction in nasal discharge of 23% over placebo for days 1 and 2 (p = 0.003).

Adult↗

The placebo needle, is it a valid and convincing placebo for use in acupuncture trials? A randomised, single-blind, cross-over pilot trial.

The issue of what constitutes an effective and realistic acupuncture placebo control has been a continuing problem for acupuncture research. In order to provide an effective placebo, the control procedure must be convincing, visible and should mimic, in all respects, apart from a physiological effect, the real active treatment. The 'Streitberger' needle might fulfil these criteria and this paper reports on a validation study. This was a single-blind, randomised, cross-over pilot study. Patients were drawn from the orthopaedic hip and knee, joint replacement waiting list. Intervention consisted of either 2 weeks of treatment with real acupuncture followed by 2 weeks on placebo, or vice versa. The prime outcome was a needle sensation questionnaire and there was a range of secondary outcomes. Thirty-seven patients were randomised and completed treatment. Groups were well balanced at baseline. No significant differences between groups or needle types were found for any of the sensations measured. Most patients were unable to discriminate between the needles by penetration; however, nearly 40% were able to detect a difference in treatment type between needles. No major differences in outcome between real and placebo needling could be found. The fact that nearly 40% of subjects did not find that the two interventions were similar, however, raises some concerns with regard to the wholesale adoption of this instrument as a standard acupuncture placebo. Further work on inter-tester reliability and standardisation of technique is highly recommended before we can be confident about using this needle in further studies.

Acupuncture Therapy↗

A placebo controlled investigation of the effects of tryptophan or placebo on subjective and objective measures of fatigue.

OBJECTIVE: To examine the effect of L-tryptophan administration on subjective and objective measures of fatigue in healthy volunteers. SUBJECTS: Six healthy volunteers (4M:2F) were recruited from staff and students at the College. SETTING: Department of Human Nutrition, St. Bartholomews and the Royal London School of Medicine and Dentistry. DESIGN: Subjects were tested for central and peripheral fatigue using a visual analogue scale, flicker fusion frequency, grip strength, reaction time and wrist ergometry. In addition, plasma free tryptophan concentrations and Trp:LNAA ratio were determined. Measurements were made before, and at 1, 2, 3 and 4 h after drinking one of two test drinks. The drinks were of either caffeine free diet Coca-Cola (placebo) or caffeine free diet Coca-Cola plus L-tryptophan (30 mg/kg: active drink). Each of the six subjects was tested after placebo and active drink with a one week washout period between test days. RESULTS: Subjective fatigue was significantly increased following tryptophan compared to placebo (P < 0.002), and objective measures of central fatigue were significantly increased by tryptophan compared to placebo (flicker fusion frequency: P < 0.001; reaction time P < 0.001). No significant changes in grip strength were found following tryptophan compared to placebo, but a significant increase in ergometric work output was seen (P < 0.001). CONCLUSION: Tryptophan ingestion in the quantity 30 mg/kg leads to increased subjective and central fatigue. Increases in work output observed following tryptophan may be as a result of a reduced perception of discomfort during ergometry.

Adult↗