A new law requires more than 92,000 health-care providers in Florida to use an electronic database that tracks patients who are prescribed controlled substances. The law is designed to reduce what is called “doctor shopping,” where substance abusers seek prescriptions for addictive drugs from multiple physicians. The Legislature also banned doctors from writing prescriptions for more than three-day supplies of controlled substances unless medically necessary. The new restrictions don’t apply to cancer patients, people who are terminally ill, and those who have suffered major trauma.