The use of polymers in different fields of modern medicine has generated significant advances in tissue engineering, diagnostic
and therapeutic strategies. Polymers have been used to control the rate of drug release, prevent toxicity, protect drugs from degradation
before delivery, target drugs to the site of action, improve absorption, bioavailability and therapeutic efficacy. Although synthetic
polymers allow producing tailor-made materials, however natural polymers exhibit the advantages of excellent biodegradability, biocompatibility,
cost-effectiveness and environmental friendliness. This review presents the current status of research and clinical applications
of natural polymers as drug delivery systems for different administration routes.