NURS 3100 Exam 1 Practice

When switching a client from IV nitroglycerin to the oral form, why is the oral dose higher?

1. The IV crosses the blood-brain barrier

2. The oral form has a decreased half-life

3. The oral form has decreased bioavailability due to the first-pass effect

4. The oral form has an increased rate of excretion

The correct answer is: The oral form has decreased bioavailability due to the first-pass effect

When switching a client from IV nitroglycerin to the oral form, the oral dose is higher because the oral form has decreased bioavailability due to the first-pass effect. The first-pass effect refers to the metabolism of a drug before it reaches systemic circulation. When a drug is taken orally, it passes through the liver before entering the systemic circulation, where some of it may be metabolized, decreasing the amount of the drug available to produce the desired effect. Therefore, a higher oral dose is needed to achieve the same therapeutic effect as the IV dose. Option A is incorrect because the statement about crossing the blood-brain barrier is not relevant to the dosing difference between IV and oral forms of nitroglycerin. Option B is incorrect because a decreased half-life would not result in a higher oral dose. Option D is incorrect because an increased rate of excretion would necessitate a higher frequency of dosing but not necessarily a higher dose.