A study led by Donald P. Tashkin, Bertrand J. Shapiro, and Ira M. Frank in 1974 was done to see the effect of delta-9 Tetrahyrdocannabinol (THC) and smoked marijuana on patients with asthma. Patients were given either a tablet containing THC or were told to smoke Marijuana and other patients were given a placebo which contained no THC. However, subjects who were given the real Marijuana and the tablet with THC were assumed to be able to identify that they were using the marijuana or tablet with THC because of its psychotropic effects. Other subjects with asthma were also given isoproterenol, a current medication for asthma using a nebulizer in order to compare the effects of THC, placebo, and smoked Marijuana. Through a series of lung function tests isoproterenol was shown to be the best bronchodilator however, THC, and smoked Marijuana also had broncho-dilating effects although they were not as strong as isoproterenol they were still significant. The effects of the bronchodilation from Marijuana and THC lasted longer than isoproterenol. The study concludes that THC and Marijuana resulted in bronchodilation effects that lasted for an average of 2 to 4 hours. However, the use of smoked Marijuana causes changes in heart rate, causes psychotropic effects, and causes an atropine-like drying effect which could affect its therapeutic usefulness.
For further reading on this study please visit: http://www.ukcia.org/research/SmokedAndOralInAsthmatic.php