Question

a nurse is caring for a client who is receiving nitroglycerin iv and is switching to the oral form of the medication. the nurse should identify that the oral dose will be higher than the iv dose for which of the following reasons? the iv form crosses the blood - brain barrier. the oral form has a decreased half - life. the oral form has decreased bioavailability because of the first - pass effect. the oral form has an increased rate of excretion.

Explanation:

To solve this, we analyze each option:

• Option 1: The ability to cross the blood - brain barrier doesn't directly relate to the dose difference between IV and oral nitroglycerin. IV and oral forms' dose difference is about bioavailability, not this barrier.
• Option 2: A decreased half - life of the oral form would not explain a higher oral dose. Half - life is about how long the drug stays in the body, not the initial dose needed.
• Option 3: Oral medications undergo first - pass metabolism in the liver, which reduces their bioavailability (the amount of drug that reaches the systemic circulation). So, to get the same therapeutic effect as the IV form (which has 100% bioavailability as it goes directly into the bloodstream), a higher oral dose is needed.
• Option 4: An increased rate of excretion would mean the drug is removed from the body faster, but it doesn't explain why a higher oral dose is needed compared to IV. The main issue with oral nitroglycerin is bioavailability due to first - pass effect, not excretion rate.

Answer:

The oral form has decreased bioavailability because of the first - pass effect.