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Metoprolol is a medication that belongs to the class of drugs known as beta blockers, and it is used to treat high blood pressure. Like most drugs, this medication can interact with other medications an individual may take, and sometimes with food or other substances as well. Some metoprolol interactions can be harmful, so it is important that the doctor recommending this medication is aware of any other drugs and supplements an individual is taking.
Medications that affect heart rhythm or blood pressure commonly lead to metoprolol interactions. Heart medications like digitalis can lead to unsafe drops in blood pressure and heart rate when taken at the same time as this drug. Reserpine, a medication that reduces levels of certain neurotransmitters, can similarly cause bradycardia, or low heart rate, when taken with metoprolol. Some anesthetics may also lead to bradycardia with this medication, especially if they are inhalation-based anesthetics.
Clonidine is another medication used to treat high blood pressure, along with some symptoms of panic disorder. It is sometimes prescribed with beta blockers, but metoprolol interactions with it can result when it is no longer taken. Metoprolol use should be stopped a few days before clonidine use ceases, in order to prevent dangerous rebound hypertension, involving a spike in blood pressure.
Another source of metoprolol interactions involve drugs that change how it is metabolized, or broken down, and excreted from the body. The antimalarial drug lumefantrine can drastically decrease how quickly metoprolol is processed in the body. In turn, this can lead to dangerously high concentrations of the beta blocker, and bradycardia can result.
Medications used to treat hypotension, such as epinephrine or arbutamine, can cause unsafe metoprolol interactions. These drugs are almost never administered at the same time, due to their opposite uses. When given simultaneously, however, they can be particularly unsafe, as the interaction can lead to dangerous increases in heart rate or blood pressure.
Some metoprolol interactions can create an increased risk of toxic interactions or harmful side effects from other drugs. This includes local anesthetics such as lidocaine, and recreational drugs such as cocaine. Both stimulant and depressant drugs may be more likely to exhibit dangerous side effects in the presence of beta blockers, so any recreational drug use should be avoided while taking this medication.
In addition, potential interactions may occur with substances not commonly thought of as drugs. Grapefruit juice contains compounds that may slow the metabolism of metoprolol, for example. This means that metoprolol may exhibit more prolonged effects if taken within an hour of drinking this juice, so caution should be used when combining the two.