The terms topical and transdermal are often used interchangeably but there is a significant difference. A topical medication is intended to have an effect at the site of application. The use of topical medications does not result in significant drug concentrations in the blood and other tissues, and causes fewer adverse reactions. Examples of topical medications include antibiotics for skin infections, corticosteroids for skin irritation, and some anesthetics. Transdermal medications are absorbed through the skin or mucosal membranes instead of by oral or injectable routes, and are intended to have an effect in areas of the body away from the site of application. Transdermal administration is an excellent method to use when a patient is unable to swallow or for medications that are significantly metabolized by the liver, and is frequently utilized for anti-nausea drugs, hormone replacement therapy, and generalized pain. When a medication is applied to the skin, whether the effect will be local, in the tissue beneath the site of application, or systemic depends on the preparation, and factors such as solubility and particle size.