Blind trials

Pyridoxine is used in morning sickness. Its mechanism of action remains unclear and several reviews of the use of pyridoxine have failed to find conclusive evidence of effectiveness. A recent double blind trial found pyridoxine to be of benefit in reducing nausea only. Some clinicians use pyridoxine as the first drug on the basis that it is the least likely to be toxic to the foetus. 

Clinical trials should be designed so as to mirtimise potential sources of bias. It is known that patients can demonstrate a positive response to treatments that they believe will benefit them, even if no pharmaceutical agent has been admrrtistered (the placebo effect ). Similarly, investigators may be biased in their observations by an expectation of particular results. To avoid such bias, blinded trial designs are used. 

Haddad AL, Matos LF, Brunstein F, et al (2003) A clinical, prospective, randomized, double-blind trial comparing skin whitening complex with hydroqui-none vs. placebo in the treatment of melasma. Int J Dermatol 42 153-156... 

A randomised, blinded, trial of clopidogrel versus aspirin in patients at risk of ischemic events (CAPRIE). CAPRIE Steering Committee. Lancet 1996 348(9038) 1329-1339. 

The first proper double blind trial of embryonic implants in 40 PD patients (20 undergoing just surgery without any implant), has shown no improvement in patients over 60 years but some clinical benefit (fewer symptoms between levodopa dosing) in those below that age. Unfortunately some of these responders eventually developed dyskinesias, a sign of too much dopamine, and further implants were halted until the technique has been re-evaluated, see Freed, CR et al. N EnglJ Med 2001, 344 710-719. 

The aim of our project was to study phloem as a source of fiber and polyphenols, and to develop a method to improve its taste without losing the potentially bioactive polyphenols. In addition, we wanted to investigate the bioavailability, cholesterolemic and antioxidative effects and safety of phloem and its phytonutrients in humans in a randomised double-blind trial. 

The randomization of a patient in a given therapy is the cornerstone of a randomized clinical trial. You may find these data in more than one place. They are often found within some form of Interactive Voice Response System (IVRS), but they may also be found in an electronic file containing the treatment assignments or on the CRF itself. If randomization data are found on the CRF, they usually consist only of the date of randomization for treatment-blinded trials. IVRS data are often found outside the confines of the clinical data management system and usually consist of the following three types of data tables. 

Buerger s disease plus arteriosclerosis obliterans (double blind trial) ... 

Why are side effects important Imagine that you have been recruited for a clinical trial of an antidepressant medication. As part of the required informed-consent procedure, you are told that you may be given a placebo instead of the active medication, but because this is a double-blind trial, you will not be told which you are getting until the study is over. You are told that... 

Grabowski J., Rhoades H., Silverman P et al. Risperidone for the treatment of cocaine dependence randomized, double-blind trial. J. Clin. Psychopharmacol. 20 305, 2000. 

Maurer M, Henn V, Dittrich A and Hofmann A (1990). Delta-9-THC shows antispastic and analgesic effects in a single-case double-blind trial. European Archives of Psychiatry and Clinical Neuroscience, 240, 1-4. 

R, Runzi M, Kron M, Kahl S, Kraus D, Jung N, Maier L, Malfertheiner P, Goebell H, Beger HG German Antibiotics in Severe Acute Pancreatitis Study Group Prophylactic antibiotic treatment in patients with predicted severe acute pancreatitis A placebo-con-trolled, double-blind trial. Gastroenterology 2004 126 997-1004. 

Alvisi A, D Ambrosi A, Onofri W, Catellani M, Palazzini E Treatment of secretory diarrhoeas. A double-blind trial of the effectiveness of rifaximin (L 105) and neomycin. Clin Trials J 1984 21 215-223. 

Solotof JI, Gudmand Hoyer E, Kreg B, Kris-tensen E, Wolff HR A double blind trial of wheat bran on symptoms of irritable bowel syndrome. Lancet 1976 i 270-272. 

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