Drug-Nutrient interaction

Question 1

Patients at higher risk for drug-nutrient interactions include:

Answer 1

1) the elderly and the very young
2) patients receiving multiple drug therapies or long-term therapy
3) patients with marginal nutritional intake
4) those with declining renal or hepatic function

Question 2

Drug therapy may impact negatively on nutritional status by altering nutrient

Answer 2

intake

- digestion/absorption
- metabolism or transport
- excretion
- requirement

Question 3

Dietary intake- can cause changes in apetite causing weight loss of weight gain

some examples of drugs that can cause this

Answer 3

o glucocorticoids

o amitriptyline, fluoxetine (antidepressants)

Question 4

Alteration of taste (e.g. metallic, salty, sweet, foul taste) – Examples:

Answer 4

o the antibiotic, clarithromycin (but note intended for short-term use).
o antineoplastic drugs. e.g. methotrexate
o prolonged dry mouth (xerostomia) caused by decreased saliva production that can decrease taste sensation and  the risk of dental caries occurs with all drugs with anticholinergic effects (the anticholinergic effects are side effects):
 tricyclic antidepressants e.g. amitriptyline, imipramine
 antipsychotic agents e.g. phenothiazines.

Question 5

Other gastrointestinal side effects:

Answer 5

o ulcerogenic e.g. nonsteroidal antiinflammatory agents (NSAIDs)
o nausea/ vomiting e.g. antineoplastic drugs, levodopa (Parkinson’s disease), ferrous salts, opioids (e.g. morphine)
o constipation e.g. narcotic agents (codeine, morphine)
o damage to the esophagus when the drug is taken without fluids . e.g. iron salts, nonsteroidal anti-inflammatory drugs [NSAID], quinidine (antimalarial, antiarrhythmic), tetracycline (antibiotic), extended release products of potassium salts, and alendronic acid and possibly other bisphosphonates (for bone replacement such as in osteoporosis).
-These drugs should be taken with lots of water and not when lying down.

Question 6

2. Digestion and Absorption

Answer 6

e. g. Proton pump inhibitors (e.g. omeprazole) are intended to interrupt acid production in the stomach, and this can have the side effect of impairing vitamin B12 absorption.
- More likely to be of significance in the elderly.
- lower production of stomach acid

e. g. Cholestyramine - used to modify serum lipids
- cholestyramine + bile salts  complex (excreted in feces)
- Therefore reduces the amount of bile salts available for fat emulsification and absorption
- Long term use of cholestyramine results in steatorrhea and decreased absorption of fat-soluble vitamins
- Less frequently used drug since GI effects often not tolerated.
- fatty stools- not used very much anymore
e. g. Cytotoxic drugs-cancer treatment
- The arrest of mitosis within the GI tract  the extent of absorption.

Question 7

3. Nutrient Metabolism

Answer 7

e. g. Isoniazid (used to treat tuberculosis) can decrease pyridoxal phosphate synthesis (by affecting the enzyme pyridoxal kinase) so that vitamin B6 metabolism is interfered with.
- pyridoxine supplements are recommended.

e. g. Warfarin (used in prevention of thromboses).
- Exerts its effect by inhibiting the hepatic reductase, which converts the storage form of vitamin K (vitamin K 2,3-epoxide) to the active form of the vitamin. i.e. acts by competitive inhibition of vitamin K activity.
- High doses of vitamin K decrease the effect of these drugs.
- Most important recommendation is to maintain consistent vitamin K intake. More details to follow on this later in term 1.

e. g. Glucocorticoids e.g. prednisone (anti-inflammatory agent) have many effects on metabolism:
- increase gluconeogenesis and decrease glucose uptake-thus elevate blood [glucose].
- decrease protein synthesis and increase protein degradation.
- other effects to be discussed later.

e.g. Antiepileptic agents e.g. phenytoin
Of chronically administered drugs, they are one of the most likely group of agents to result in marked folate deficiency.
-Mechanism is increased folate turnover (enzyme induction)
-Advise folate-rich foods or small doses (multivitamin) of folic acid supplement

Question 8

Glucocorticoids

Answer 8

e. g. prednisone (anti-inflammatory agent) have many effects on metabolism:
- increase gluconeogenesis and decrease glucose uptake-thus elevate blood [glucose].
- decrease protein synthesis and increase protein degradation.
- other effects to be discussed later.

Question 9

e.g. Antiepileptic agents e.g. phenytoin

Answer 9

• Of chronically administered drugs, they are one of the most likely group of agents to result in marked folate deficiency.
• Mechanism is increased folate turnover (enzyme induction)
• Advise folate-rich foods or small doses (multivitamin) of folic acid supplement

Question 10

4. Excretion (See Table 11.6 for other examples)

Answer 10

e. g. Interaction between diuretics and K.
- The diuretics are intended to increase urinary Na and water excretion, but an unwanted side effect of some diuretics is increased urinary K excretion or decreased urinary K excretion.

Diuretics fall under these categories:

a) potassium-sparing
- avoid K+ supplements, salt substitutes
- be moderate in use of foods rich in K+ while recognizing the importance of K in a balanced diet
b) potassium-depleting
- Diet rich in K+-containing foods.