Introduction Pharmacology is the study of drugs in the human body. Analysing the uses, mechanisms, actions, and adverse events a drug may have once administered to determine the safety and efficacy of the drug.

Scientists thoroughly research compounds to look at the structure, pharmacokinetics, and physicochemical properties to be able to develop a good drug (Battista and Yassin, 2011). (29) Many of these are an improvement upon existing compounds which have been chemically modified to enhance the activity of the drug. The chemical modification of ?-blockers propranolol to atenolol is a key example of how small changes can result in large effects.

?-blockers are widely used drugs and are known for their properties to treat cardiovascular diseases such as coronary heart disease and hypertension (Borchard, 1998) (18). ?-blockers have ?1/ ?2 selectivity, or cardio-selectivity, where the compound will have an affinity for either ?1 (located in the heart) or ?2 receptors (located in bronchial or vascular smooth muscle) (Poirier and Tobe, 2014). (27) Selective ?-blockers will have an affinity for ?1 receptors over ?2, such as atenolol and non-selective ?-blockers will have an affinity for both, such as propranolol (Quirke, 2006; Smith et al., 2012; Wiysonge et al., 2017). (16,17,12)