CDN Pharmacology & Drug-Nutrient Interactions 2

Question 1

Absorption of levothyroxine is significantly decreased when the medication is taken concurrently with which mineral supplement?

Accepted Answer

Calcium

Answer

Calcium (as carbonate or citrate) binds levothyroxine in the gastrointestinal tract, reducing its bioavailability by up to 40%.

Question 2

Long-term corticosteroid therapy increases the risk of deficiency in which combination of nutrients, contributing to osteoporosis risk?

Accepted Answer

Calcium and Vitamin D

Answer

Corticosteroids decrease intestinal calcium absorption, increase renal calcium excretion, and impair vitamin D metabolism, necessitating supplementation.

Question 3

High-dose niacin supplementation used to raise HDL cholesterol requires monitoring for which serious adverse effect?

Accepted Answer

Hepatotoxicity

Answer

Sustained-release or high-dose niacin can cause dose-dependent hepatotoxicity, requiring periodic monitoring of liver function tests.

Question 4

Chronic use of the anticonvulsant phenytoin (Dilantin) is associated with decreased levels of which nutrient due to impaired absorption and accelerated catabolism?

Accepted Answer

Folate

Answer

Phenytoin impairs intestinal folate absorption and induces hepatic enzymes that accelerate folate catabolism, increasing the risk of megaloblastic anemia.

Question 5

Which herbal supplement is known to induce CYP450 enzymes, potentially reducing the effectiveness of oral contraceptives and other medications?

Accepted Answer

St. John's Wort

Answer

St. John's Wort (Hypericum perforatum) strongly induces CYP3A4 and P-glycoprotein, leading to reduced plasma levels of many drugs including hormonal contraceptives.

(CDN) Certified Dietician Nutritionist Practice Test

(CDN) Certified Dietician Nutritionist Practice Test

CDN Pharmacology & Drug-Nutrient Interactions 2