A nurse is reviewing laboratory results of a client who has atrial fibrillation and is taking warfarin. For which of the following results should the nurse notify the provider?

Choice A reason: Taking the medication in the morning is not the correct instruction. Simvastatin is a statin drug that lowers cholesterol levels by inhibiting the enzyme that produces cholesterol in the liver. The liver produces more cholesterol at night, so simvastatin is more effective when taken in the evening or at bedtime.

Choice B reason: Avoiding grapefruit juice is the correct instruction. Grapefruit juice can increase the blood levels of simvastatin and cause serious side effects such as muscle damage, liver damage, and kidney failure. Grapefruit juice inhibits the enzyme that metabolizes simvastatin in the intestine, leading to higher concentrations of the drug in the bloodstream.

Choice C reason: Monitoring for ringing in the ears is not the correct instruction. Ringing in the ears, or tinnitus, is not a common or serious side effect of simvastatin. However, some other medications that lower cholesterol, such as niacin and gemfibrozil, can cause tinnitus. The client should report any unusual or persistent symptoms to the prescriber.

Choice D reason: Expecting brown-colored urine is not the correct instruction. Brown-colored urine, or hematuria, is not a normal or expected side effect of simvastatin. However, it may indicate a serious condition such as rhabdomyolysis, which is a rare but life-threatening complication of statin therapy. Rhabdomyolysis is the breakdown of muscle tissue that releases a protein called myoglobin into the bloodstream. Myoglobin can damage the kidneys and cause brown-colored urine. The client should seek immediate medical attention if they notice any signs of rhabdomyolysis, such as muscle pain, weakness, fever, or dark urine.

Choice A reason: Bradycardia is not an adverse effect of diphenhydramine. Bradycardia is a slow heart rate, usually below 60 beats per minute. Diphenhydramine is an antihistamine that blocks the effects of histamine, a chemical that causes allergic reactions. Diphenhydramine does not affect the heart rate, although it may cause palpitations or irregular heartbeat in some cases.

Choice B reason: Constipation is an adverse effect of diphenhydramine. Constipation is a condition in which the bowel movements are infrequent, hard, or difficult to pass. Diphenhydramine has anticholinergic properties, which means it inhibits the activity of acetylcholine, a neurotransmitter that regulates the smooth muscle contraction in the gastrointestinal tract. Diphenhydramine can reduce the intestinal motility and cause constipation, as well as dry mouth, blurred vision, and urinary retention.

Choice C reason: Hypertension is not an adverse effect of diphenhydramine. Hypertension is a condition in which the blood pressure is abnormally high, usually above 140/90 mmHg. Diphenhydramine does not affect the blood pressure, although it may cause orthostatic hypotension, which is a sudden drop in blood pressure when changing positions from lying to standing. This can cause dizziness, fainting, or falls.

Choice D reason: Sedation is an adverse effect of diphenhydramine. Sedation is a state of reduced alertness, awareness, or responsiveness. Diphenhydramine can cross the blood-brain barrier and affect the central nervous system, causing drowsiness, fatigue, impaired coordination, and reduced mental performance. Diphenhydramine can also potentiate the effects of alcohol and other sedatives, such as benzodiazepines, opioids, or barbiturates. The nurse should advise the client to avoid driving, operating machinery, or performing other tasks that require attention and concentration while taking diphenhydramine.