Pharmacology is a scientific discipline that described the overt effects of biologically active chemicals, pharmacology now explores the molecular mechanisms by which drugs cause biological effects. In other words pharmacology is the study of how chemical agents, both natural and synthetic (i.e., drugs) affect biological systems. This comprises investigation of the derivation, chemical properties, physiological and behavioral effects, mechanisms of action, biological transformations, and the therapeutic and non-therapeutic uses of drugs. Pharmacological studies can determine the effects of chemical agents upon subcellular, systemic, physiological or behavioral processes; focus on the treatment and prevention of diseases. Symptom relief in palliative care often presents challenges to the prescriber, and the evidence to guide choice of treatments is often derived from experience rather than controlled trials. Palliative care services have comprehensive guidelines for symptom control, often advising use of drugs for unlicensed indications. Awareness of emotional, psychological and social contributors to symptoms will help to guide strategies for management.