Anti-emetic drugs are usually prescribed to suppress vomiting. They are found in many travel sickness pills. Opiates have a tendency to induce vomiting, particularly when they are injected. This has led some drug users to combine anti-emetic drugs with opiates to enhance the pleasurable effect. Cannabis has been found by some people to be an effective anti-emetic in coping with the side effects of chemo-therapy used in cancer treatment.