Toxicity of marijuana and tobacco smoking in the beagle.

Four cigarettes of marijuana or tobacco in the form of smoke inhaled into the trachea were administered to dogs daily over a period of nine months. Marijuana caused a slowing of body weight gain. Food consumption increased at first and was accompanied by diarrhea; then it decreased. This suggests a malabsorption of food or a more fundamental metabolic disturbance. The tobacco smoking group consumed much less food without showing any significant change in body weight gain in 3 and 6 months, but it did in 9 months only. In marijuana smoking dog, blood pressure remained unchanged. The resting heart rate was increased (by 32% at 3, 30% at 6, and 15% at 9 months). Alpha1-globulin, eosinophils and lymphocyte count were significantly decreased. A decrease in serum triglycerides was noted. In addition, a behavioral study permitted us to note a general perturbation in the behaviour of the marijuana smoking dogs. The dogs showed impairment of learning, probably due to these behavioral perturbations.