Can drugs be transfered to animals through human contact?

No Actually yes but the contact has to be rather intimate. Human and animal skin is a pretty effective barrier and getting a drug passed both is very unlikely and high concentrations will not be effected. HOWEVER is you let your dog lick the inside of your mouth (or do other equally or even grosser things) than the concentration of transfer will go up. An interesting point of trivial - in not so medievil times they would soak a piece of bread with the urine of a supposide witch and if the dog went crazy as well then the witch was really a witch and they would burn her. In actual fact the phenomina is a result of ergot poisoning (a nasty group of drugs and poisons to which LSD belongs). Ergot is a fungal infection of grain. The fungus wants to eat the grain and to deter other creatures from eating it - so it growing the poisons. When ergot tainted grain is used to make bread whole communities can suffer.