A nurse is reviewing the medical record for a client who has a new prescription for phenytoin. Which of the following statements from the medical record should the nurse identify as a contraindication for the administration of phenytoin?
The client has a history of sinus bradycardia.
The client has a history of cholecystitis.
The client takes vitamin B12 supplements.
The client takes ibuprofen.
The Correct Answer is A
Phenytoin is a hydantoin anticonvulsant that stabilizes neuronal membranes by delaying the influx of sodium ions during action potentials. It has a narrow therapeutic index and significant effects on cardiac conduction, specifically lengthening the refractory period. Due to its potential to depress myocardial automaticity, it is strictly avoided in patients with certain pre-existing conduction system abnormalities.
Rationale:
A. Sinus bradycardia is a major contraindication for phenytoin because the drug can further depress cardiac conduction and automaticity. Phenytoin possesses class IB antiarrhythmic properties, which can lead to severe cardiovascular collapse or heart block in patients with slow heart rates. Administering this drug to a bradycardic patient poses a life-threatening risk of asystole.
B. A history of cholecystitis, or inflammation of the gallbladder, does not contraindicate the use of phenytoin for seizure management. While phenytoin is metabolized by the liver, it does not have a direct impact on gallbladder function or the formation of gallstones. The nurse would prioritize monitoring liver enzymes rather than focusing on a history of cholecystitis.
C. Taking vitamin B12 supplements does not prevent a patient from receiving phenytoin, as there is no dangerous interaction between the two. Interestingly, long-term phenytoin use is actually associated with folate deficiency rather than issues with B12. Supplements are generally safe and may be necessary for patients with concurrent nutritional deficiencies during anticonvulsant therapy.
D. Ibuprofen is a non-steroidal anti-inflammatory drug that does not have a documented clinical contraindication with the administration of phenytoin. While phenytoin has many drug-drug interactions involving the cytochrome P450 system, ibuprofen is not typically one that causes toxicity. The nurse can safely administer both medications as long as standard monitoring is performed.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is A
Explanation
Total parenteral nutritioncontains high concentrations of glucose, which stimulates the pancreas to secrete significant amounts of insulin. Abrupt cessation of this hypertonic solution can lead to a rapid drop in blood glucose levels, resulting in rebound hypoglycemia. Maintaining a consistent dextrose source is critical until the next TPN bag is prepared.
Rationale:
A.Dextrose 10% in water (D10W) is the appropriate fluid to administer because it provides enough glucose to prevent rebound hypoglycemia when TPN is unavailable. The patient's pancreas is primed to release high levels of insulin in response to the TPN; without a continued dextrose source, the patient's blood sugar will plummet. D10W serves as a temporary bridge to maintain glycemic stability.
B.0.9% sodium chloride is an isotonic solution that provides volume and electrolytes but contains no glucose. Administering this fluid alone would fail to prevent the severe hypoglycemia that occurs when the high-glucose TPN infusion is suddenly stopped. While it is useful for many clinical situations, it is inappropriate as a substitute for TPN in a patient requiring glucose maintenance.
C.0.45% sodium chloride is a hypotonic solution used for cellular dehydration and does not contain the calories or sugar necessary to counteract the patient's high insulin levels. Using this solution when TPN runs out would leave the patient vulnerable to symptomatic hypoglycemia and potential neurological complications. It is an inadequate substitute for the high dextrose concentration required by the patient's current metabolic state.
D.Lactated Ringer's is a balanced crystalloid solution used for fluid resuscitation and electrolyte replacement, but it contains negligible amounts of carbohydrate. It cannot maintain the blood glucose levels of a patient who has been receiving hypertonic TPN. The nurse must prioritize a dextrose-containing solution to avoid the life-threatening consequences of a sudden cessation of parenteral nutrition support.
Correct Answer is ["15"]
Explanation
Step 1 is to identify the ordered dose per kg, the client's weight in kg, and the available concentration
Ordered Dose: 30 mg/kg
Client weight: 20 kg
Available Concentration: 200 mg / 5 mL
Step 2 is to calculate the total dose in milligrams (mg) required for the child
Total mg dose = weight in kg × dosage (mg/kg)
Total mg dose = 20 × 30
20 × 30 = 600
Total mg dose = 600 mg
Step 3 is to calculate the volume to administer in milliliters (mL)
Volume = (Total mg dose ÷ Available dose) × Available volume
Volume = (600 ÷ 200) × 5
600 ÷ 200 = 3
3 × 5 = 15
Volume to administer = 15 mL
Step 4 is to round to the nearest whole number
15 = 15
Answer: 15 mL
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