Homeopathy is based on the principle of 'like cures like' for example in cases of insomnia, a drug would be prescribed to induce an artificial sleep, sometimes causing unwanted side effects such as daytime somnolence or addiction. In homeopathy a minute dose of a substance, such as coffee may be prescribed, which in large doses causes insomnia in a healthy person. Homeopathically this substance has been known to alleviate the symptoms of insomnia for example in cases of jetlag.