Which organ is primarily responsible for excretion of a medication?

Choice A reason: This is incorrect. Miosis is the constriction of the pupils, which can also be caused by morphine, but it is not a life-threatening side effect. Miosis occurs because morphine stimulates the parasympathetic nervous system, which controls the muscles that constrict the pupils¹.

Choice B reason: This is incorrect. Sedation is the state of being calm, relaxed, and sleepy, which can also be caused by morphine, but it is not a life-threatening side effect. Sedation occurs because morphine depresses the central nervous system, which reduces the activity of the brain and the body.

Choice C reason: This is correct. Respiratory depression is the slowing down of breathing, which can be a life-threatening side effect of morphine. Respiratory depression occurs because morphine depresses the respiratory center in the brainstem, which regulates the rate and depth of breathing. If the breathing becomes too slow or shallow, the patient may not get enough oxygen and may lose consciousness or die.

Choice D reason: This is incorrect. Euphoria is the feeling of intense happiness, pleasure, or wellbeing, which can also be caused by morphine, but it is not a life-threatening side effect. Euphoria occurs because morphine stimulates the reward system in the brain, which releases dopamine, a neurotransmitter that causes positive emotions.

Choice A reason: This is correct. The kidneys are the main organs for excreting water-soluble substances, including most drugs and their metabolites. The kidneys filter the blood and remove waste products and excess fluid as urine. Drugs can be excreted by glomerular filtration, tubular secretion, or tubular reabsorption.

Choice B reason: This is incorrect. The pancreas is not involved in excretion of drugs. The pancreas is an organ that produces digestive enzymes and hormones, such as insulin and glucagon.

Choice C reason: This is incorrect. The gallbladder is not involved in excretion of drugs. The gallbladder is an organ that stores and concentrates bile, a fluid that helps digest fats.

Choice D reason: This is incorrect. The liver is not primarily responsible for excretion of drugs, although it plays an important role in drug metabolism. The liver is an organ that performs many functions, such as detoxifying substances, synthesizing proteins, and producing bile. The liver can transform drugs into more polar and water-soluble compounds, which can then be excreted by the kidneys or the biliary system.