Medication Interactions and Safety: Practice Questions
Learn how food, medicines, and other products can alter medication effects, create additive risks, or make a combination unsafe, and when to seek professional guidance.
How interactions create risk
Medication interactions can increase or decrease a medicine’s effects, or cause unexpected harm. They can involve prescription medicines, over-the-counter products, supplements, foods, and drinks.
When reviewing a combination, consider whether it may change drug levels, create such as sedation, low blood pressure, or bleeding, or involve a combination. If uncertain, check with a pharmacist or prescriber before combining products. These examples do not replace a review of a person’s complete medication list, and a medicine should not be started, stopped, or changed based only on them.
Grapefruit and simvastatin
Grapefruit can increase the amount of some medicines, including simvastatin, that enters the blood. Higher drug levels may increase side effects, including muscle injury. Grapefruit does not interact with every statin in the same way, so check the specific medicine’s label and ask a pharmacist or prescriber whether to avoid grapefruit or choose another option.
Warfarin and leafy greens
Kale and spinach contain , which can reduce warfarin’s effect. A sudden increase in intake may change anticoagulation, so consistency is generally the key: discuss major diet changes with the care team and follow recommended blood-test monitoring rather than making abrupt changes or automatically avoiding nutritious foods.
Opioids and benzodiazepines
Oxycodone and alprazolam can both depress the central nervous system, so their effects can add together. Taking them together can cause extreme sedation and dangerously slow or difficult breathing, coma, or death.
This combination requires prescriber oversight. Do not combine these medicines on your own or add alcohol or other sedating medicines. Trouble breathing or inability to stay awake requires emergency help.
Sildenafil and nitroglycerin
Sildenafil must not be combined with organic nitrates such as nitroglycerin. The combination is because it can cause a dangerous drop in blood pressure.
Contact a prescriber for advice about treatment options. If emergency care is needed, tell clinicians if sildenafil was taken recently before receiving nitrate treatment.
Warfarin and naproxen
Naproxen is an . Combining NSAIDs with anticoagulants such as warfarin can increase the risk of serious bleeding.
Check with a pharmacist or prescriber before taking naproxen with warfarin. Do not assume that an over-the-counter medicine is free of interactions.