herb drug interactions

Question 1

Less than 40% of patients reveal use of herbal dietary
supplements to their physicians or other heath care
professionals, why?

Answer 1

▪ Physicians do not commonly ask patients about their
complementary and alternative medicine (CAM) use.

▪ Patients may think it not to be sufficiently important.

▪ Patients my think that the physician would not understand
the reasons for their taking CAM.

▪ Fear of disapproval

Question 2

study table page 5

Question 3

what are some difficulties of interpreting herb drug interactions

Answer 3

▪ Patients do not reveal the use of herbal products.
▪ Standard system for interaction prediction and evaluation
is nonexistent
▪ Human genetics cause variability in metabolism.
▪ Content and dosage form variability of herbal products.

Question 4

what is the first major herb drug interaction report

Answer 4

In Canada 1996, during a study to evaluate felodipine
interaction with alcohol, the plasma concentrations of the
drug in the placebo group that had received grapefruit
juice rather than alcohol, were surprisingly high.

In a follow-up study using either grapefruit juice or orange juice;
the grapefruit juice increased the bioavailability of felodipine
by an average of 284%; 3 times the amount in the blood of
those who consumed grapefruit juice as those who consumed
water.

Mechanism: the major metabolic enzyme CYP3A4 is inhibited,
thus preventing the drug from being metabolized before it
enters the blood stream.
▪ This effect was later attributed to the presence of
furanocoumarins (e.g. bergamottin).

Question 5

what are the MOA of drug herb interactions

Answer 5

Two types of herb-drug interactions can be ascribed:
1. Pharmacodynamic Interactions: involve botanicals and
conventional medications that enhance or negate each
other’s effects as a result of similar or disparate
pharmacological activity, respectively.
2. Pharmacokinetic Interactions: arise from the ability of
phytochemicals or conventional drugs to modulate the
activity of xenobiotic metabolizing enzymes and/or
various drug transporters.

Question 6

what are pharmacokinetics interactions

Answer 6

Alteration of absorption (GI motility, gastric pH,
intestinal metabolism), distribution (increase or decrease
the protein binding), metabolism (inhibition or induction
of metabolic enzymes or drug transporters), or
elimination of a conventional drug by an herbal product
or other dietary supplements.

Question 7

how to prevent herb drug interactions?

Answer 7

Take a complete and accurate medication history by asking
patients about their use of herbs.
▪ Obtain brand names and exact lists of ingredients and
dosages.
▪ Ask patients to bring supplement containers, if possible.
▪ Check for interaction information from multiple sources:
No interactions known: does not mean that no interactions exist.
Educate patients to avoid sudden changes in supplements:
stopping, starting, or switching brands.
▪ Stability is not guaranteed; manufacturers may change
ingredients or quality at any time.
▪ Educate patients to watch for symptoms that would indicate
a possible developing interaction.