Morphine is the most important pharmacologically active ingredient in opium, the resin obtained from the dried juice of the opium poppy. More than 200 years ago, morphine established itself in clinical practice. It is the first model of opioid medicine, whose analgesic and satisfying influences are mediated by the activation of opioid receptors which are fundamentally located within the central nervous system (CNS). The World Health Organization (WHO) has proposed that morphine continue to be the strong opioid of choice for the treatment of patients with moderate to severe cancer pain. Pharmacology Endorphins, enkephalins and dynorphins are endogenous opioids. Morphine works by imitating endorphins responsible for reducing pain, producing drowsiness and feelings of pleasure. Morphine is a standard of narcotic medicine and is the standard against which all other opioids are examined. It interacts mainly with the μ-opioid receptor. These μ-combining locations are discretely dispersed throughout the brain and in some cortical areas. They are also found on the axon terminals of primary afferents within lamina I and II of the spinal cord and in the spinal nucleus of the trigeminal nerve.[24] Morphine is an opioid receptor agonist of the alkaloid phenanthrene. ''It is a weak base with a PKa 7.9 at physiological PH, 76% of its molecules are ionized'' and it is relatively soluble in water and poorly lipid-soluble. The main effect of morphine is the contact and activation of μ-opioid receptors in the central nervous system. The basic pharmacological effect of morphine applies in the clinical setting on the (CNS) and gastrointestinal tract (GIT). It has two main actions in its therapeutic effect which are analgesia and sedation. Morphine is also an agonist at κ and δ opioid receptors, the action of κ opioids...... half of the article ...... before the onset of action compared to NR modulations. There are two preparations per day with an initial action of 1-2 hours and which reach the peak intensity of the drug at 4 hours. The once-daily MR preparation has a slower initial onset of action and reaches peak levels at 8.5 hours. The beneficial effects of morphine are many, due to the reduced perception of pain, the decrease in the reaction to pain and the increase in pain tolerance. In contrast, the most widely recognized side effects are sedation, respiratory depression and constipation, as well as nausea and vomiting, while there are other common ones such as tolerance, physical and psychological dependence. All of these adverse effects of morphine can be reduced with five possible methods that decrease the dose, alter the route of administration, and use some adjuvant drugs, as well as opioid rotation and symptomatic management of adverse effects.