Peripherally selective drug

Peripherally selective drugs have their primary mechanism of action outside of the central nervous system (CNS), usually because they are excluded from the CNS by the blood-brain barrier. By being excluded from the CNS, drugs may act on the rest of the body without producing side-effects related to their effects on the brain or spinal cord. For example, most opiates cause sedation when given at a sufficiently high dose, but peripherally selective opiates can act on the rest of the body without entering the brain and are less likely to cause sedation.