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: Peak level is the correct term to describe the highest concentration of a drug in the blood after it is administered. Peak level is also known as peak plasma concentration or Cmax, and it reflects the rate and extent of drug absorption. Peak level is influenced by factors such as the route of administration, the dose, the formulation, and the bioavailability of the drug. Peak level is important to monitor for drugs that have a narrow therapeutic range, meaning that there is a small difference between the effective and toxic doses. The nurse should measure the peak level at the appropriate time after the drug administration, and adjust the dose or the frequency as needed to achieve the desired therapeutic effect and avoid adverse effects .

Choice B reason: Halflife is not the correct term to describe the highest concentration of a drug in the blood after it is administered. Halflife is the time it takes for the concentration of a drug in the blood to decrease by 50%. Halflife reflects the rate of drug elimination, which depends on factors such as the metabolism and excretion of the drug. Halflife is important to determine the dosing interval and the time to reach steady state. The nurse should consider the halflife of the drug when prescribing or administering the drug, and avoid drug accumulation or subtherapeutic levels .

Choice C reason: Trough level is not the correct term to describe the highest concentration of a drug in the blood after it is administered. Trough level is the lowest concentration of a drug in the blood before the next dose is given. Trough level reflects the balance between drug absorption and elimination, and it indicates the minimum effective concentration of the drug. Trough level is important to monitor for drugs that have a narrow therapeutic range, meaning that there is a small difference between the effective and toxic doses. The nurse should measure the trough level just before the next dose of the drug, and adjust the dose or the frequency as needed to achieve the desired therapeutic effect and avoid adverse effects .

Choice D reason: Steady state is not the correct term to describe the highest concentration of a drug in the blood after it is administered. Steady state is the condition when the rate of drug administration is equal to the rate of drug elimination, and the concentration of the drug in the blood remains constant. Steady state is usually reached after four to five halflives of the drug, and it reflects the optimal therapeutic level of the drug. Steady state is important to maintain for drugs that have a long halflife or a narrow therapeutic range, meaning that there is a small difference between the effective and toxic doses. The nurse should ensure that the drug is administered at regular intervals and at the appropriate dose to achieve and maintain steady state.