Drug repurposing, also referred to as drug repositioning or drug reprofiling, is a scientific
approach to the detection of any new application for an already approved or investigational drug. It
is a useful policy for the invention and development of new pharmacological or therapeutic applications
of different drugs. The strategy has been known to offer numerous advantages over developing
a completely novel drug for certain problems. Drug repurposing has numerous methodologies
that can be categorized as target-oriented, drug-oriented, and problem-oriented. The choice of the
methodology of drug repurposing relies on the accessible information about the drug molecule and
like pharmacokinetic, pharmacological, physicochemical, and toxicological profile of the drug. In
addition, molecular docking studies and other computer-aided methods have been known to show
application in drug repurposing. The variation in dosage for original target diseases and novel diseases
presents a challenge for researchers of drug repurposing in present times. The present review
critically discusses the drugs repurposed for cancer, covid-19, Alzheimer’s, and other diseases,
strategies, and challenges of drug repurposing. Moreover, regulatory perspectives related to different
countries like the United States (US), Europe, and India have been delineated in the present review.