A patient is prescribed Flexeril (cyclobenzaprine) for muscle spasms. Which of the following is the most common side effect that the nurse should educate the patient about?

Choice A reason: This is incorrect. Antibiotics are not a term for a drug model, but a class of drugs that are used to treat bacterial infections. Antibiotics can have different chemical structures, mechanisms of action, and modes of action. For example, penicillin is a prototype drug of the beta lactam antibiotics, which inhibit the synthesis of bacterial cell walls¹.

Choice B reason: This is incorrect. Pharmacologic drug is not a term for a drug model, but a general term for any substance that has a physiological effect on the body. Pharmacologic drugs can belong to different classes, such as analgesics, antihistamines, or antivirals. For example, aspirin is a prototype drug of the nonsteroidal anti-inflammatory drugs (NSAIDs), which reduce pain, inflammation, and fever.

Choice C reason: This is correct. Prototype drug is the term used for a well understood drug model with which other drugs in its representative class are compared. A prototype drug is an individual drug that has similar chemical structure, mechanism of action, and mode of action as other drugs in its class. A prototype drug is often the first developed or the most important drug in its class, and is used as a reference for comparison. For example, morphine is a prototype drug of the opioid analgesics, which relieve pain by binding to opioid receptors in the brain and spinal cord.

Choice D reason: This is incorrect. Therapeutic drug is not a term for a drug model, but a term for any drug that is used to treat or prevent a disease or disorder. Therapeutic drugs can belong to different classes, such as antibiotics, antihypertensives, or antidepressants. For example, metformin is a prototype drug of the biguanide antidiabetic drugs, which lower blood glucose levels by reducing glucose production in the liver and increasing glucose uptake in the muscles.

Choice A reason: This is correct. The liver is the main organ responsible for drug metabolism. The enzymes that the body uses to metabolize drugs are present throughout the body but are most abundant in the liver. The liver can transform drugs into more polar and water-soluble compounds, which can then be excreted by the kidneys or the biliary system.

Choice B reason: This is incorrect. The lungs are not primarily responsible for drug metabolism, although they can play a minor role in some cases. The lungs can metabolize some drugs that are inhaled, such as anesthetics, or drugs that circulate through the pulmonary blood vessels, such as propranolol. However, the lungs have a lower capacity and a lower variety of enzymes than the liver.

Choice C reason: This is incorrect. The heart is not responsible for drug metabolism, although it can be affected by it. The heart is the organ that pumps blood throughout the body, delivering oxygen and nutrients to the tissues and organs. The heart can be influenced by the pharmacokinetics and pharmacodynamics of drugs, which are the processes of drug absorption, distribution, metabolism, and excretion, and the effects of drugs on the body, respectively.

Choice D reason: This is incorrect. The kidney is not primarily responsible for drug metabolism, although it is important for drug excretion. The kidney is the organ that filters the blood and removes waste products and excess fluid as urine. The kidney can excrete drugs that are water-soluble or that are not reabsorbed by the tubules. The kidney can also metabolize some drugs, such as aspirin, but to a lesser extent than the liver.