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Table 2 Potential herb-drug interactions (HDIs), severity and mechanism identified among respondents reporting the use of herbal and natural products with prescription medicines (n = 181)

From: Pregnancy, prescription medicines and the potential risk of herb-drug interactions: a cross-sectional survey

Herbal/Natural Product

Prescribed Medicine

Interaction Rating

Mechanism of Interaction

Aloe (12)

Insulin (1)

Moderate

Additive effects, lower blood glucose levels lead to increased risk of hypoglycaemia.

Chamomile (29)

Diazepam (1)

Moderate

Additive effects of benzodiazepines, lead to increased risk of CNS depression, psychomotor impairment.

Propranolol (1)

Moderate

Inhibition of CYP1A2 and CYP2D6 (in vitro and in vivo). Increase levels of drugs metabolized by this enzyme.

Diclofenac (1)

Moderate

Inhibition of CYP2C9 (in vitro). Increase levels of drugs metabolized by this enzyme.

Ondansetron (1)

Minor

Inhibition of CYP1A2 (in vitro and in vivo). Increase levels of drugs metabolized by this enzyme.

Chlorpromazine (1)

Moderate

Inhibition of CYP2D6 (in vitro). Increase levels of drugs metabolized by this enzyme.

Dyhidrocodeine (2)

Moderate

Additive effects of codeine, lead to increased risk of CNS depression, psychomotor impairment.

Co-codamol (1)

Moderate

Additive effects of codeine, lead to increased risk of CNS depression, psychomotor impairment.

Cranberry (42)

Diazepam (1)

Moderate

Inhibition of CYP2C9 (in vitro), contradictory results in clinical research. Increase levels of drugs metabolized by this enzyme.

Diclofenac (1)

Moderate

Inhibition of CYP2C9 (in vitro), contradictory results in clinical research. Increase levels of drugs metabolized by this enzyme

Fish oil (24)

Progesterone pessaries (2)

Moderate

Progesterone may interfere with the triglyceride lowering effects of fish oils.

Dalteparin (2)

Moderate

Additive effects, lead to increased risk of bleeding.

Enoxaparin (1)

Moderate

Additive effects, lead to increased risk of bleeding.

Labetolol (2)

Moderate

Additive effects with antihypertensive, lead to increased risk of hypotension.

Methyldopa (1)

Moderate

Additive effects with antihypertensive, lead to increases risk of hypotension.

Ginger (50)

Metformin (1)

Moderate

Additive effects, might increase insulin level and/or decrease blood glucose levels, may lead to hypoglycemia.

Insulin (2)

Moderate

Additive effects, might increase insulin level and/or decrease blood glucose levels, may lead to hypoglycemia.

Aspirin (4)

Moderate

Inhibit thromboxane synthetase and decrease platelet aggregation lead to increased risk of bleeding.

Nifedipine (1)

Major

Significantly inhibits platelet aggregation, synergetic effects, may lead to potential cardiovascular and cerebrovascular complications.

Ginseng (4)

Metformin (1)

Moderate

Additive effects, might increase insulin level and/or decrease blood glucose levels, may lead to hypoglycemia.

Diazepam (1)

Moderate

Additive effects of benzodiazepines, lead to increased risk of CNS depression, psychomotor impairment

Grapefruit (8)

Itraconazole (1)

Moderate

Might affect absorption and might increase or decrease itraconazole levels.

Propranolol (1)

Moderate

Inhibition of CYP1A2 (preliminary evidence). Increase levels of drugs metabolized by this enzyme.

Diclofenac (1)

Moderate

Inhibition of CYP2C9 (preliminary evidence), contradictory results in clinical research. Increase levels of drugs metabolized by this enzyme.

Omeprazole (1)

Moderate

Inhibition of CYP2C19 (preliminary evidence), contradictory results in clinical research. Increase levels of drugs metabolized by this enzyme.

Sage (1)

Co-codamol (1)

Moderate

Inhibition of CYP2D6 (in vitro). Increase levels of drugs metabolized by this enzyme.