What happens when you take metoprolol with hawthorn?
Metoprolol is a beta-1 selective blocker that lowers heart rate and blood pressure by blocking adrenaline at cardiac beta-1 receptors. Hawthorn (Crataegus monogyna or Crataegus laevigata) is an herbal extract from the berries, leaves, and flowers of the hawthorn shrub, traditionally used for heart failure and mild blood-pressure support. Modern hawthorn extracts (commonly standardized to flavonoids and oligomeric procyanidins) have several measurable cardiovascular effects: mild vasodilation through nitric oxide pathways, small positive inotropic action increasing the force of cardiac contraction, mild reduction in heart rate, and modest reductions in systolic and diastolic blood pressure.
When hawthorn is added to metoprolol, those effects stack on top of the beta-blocker's own action. The interaction is pharmacodynamic, meaning it happens at the receptor and tissue level rather than through changes in how each substance is metabolized. Hawthorn does not change metoprolol absorption or clearance, and metoprolol does not change hawthorn's bioactivity. The combined effect is additive: blood pressure tends to drop further, heart rate to slow a little more, and in some patients dizziness, lightheadedness on standing, or fatigue appear.
The size of the effect varies. In healthy adults with a baseline blood pressure of 140/90, the additive drop is usually mild and well tolerated. In patients already running close to 110 systolic, or those on two or three other antihypertensives, the same addition can drop blood pressure into a range that triggers dizziness or falls.
Why is this important?
Hawthorn has a generally favorable safety profile when used alone. A 2008 Cochrane review of 14 trials in heart failure patients found that hawthorn produced small symptom improvements and was well tolerated, with mild side effects including dizziness, nausea, and gastrointestinal upset. The 2006 SPICE trial randomized 2,681 heart failure patients to hawthorn or placebo and found no overall mortality benefit but no major safety signal either.
The interaction risk with metoprolol is not from hawthorn being intrinsically dangerous; it is from the cumulative cardiovascular depression when two effective heart-rate-lowering and blood-pressure-lowering agents are stacked. Older adults, patients with autonomic dysfunction or diabetes, and patients on multi-drug antihypertensive regimens are the highest-risk groups. Falls in older adults from drug-induced hypotension are a major cause of hospitalization, hip fracture, and loss of independence.
The fact that the interaction is pharmacodynamic and not metabolic means dose-spacing does not help. Taking hawthorn at noon and metoprolol at breakfast does not prevent the additive blood pressure effect, because both reach the cardiovascular system through systemic exposure.
What should you do?
Do not add hawthorn to your medication regimen if you take metoprolol without first discussing it with your cardiologist or primary care provider. The right answer depends on what metoprolol was prescribed for, what your current blood pressure and heart rate look like, and whether you take any other cardiovascular medications.
If your prescriber agrees that hawthorn is reasonable to try, plan to monitor home blood pressure and pulse twice daily for at least the first four to six weeks. Look for systolic pressure dropping below your goal (often below 110 to 120 in older or fragile patients), resting heart rate falling below 55 to 60, or new symptoms of dizziness on standing, fatigue, or fainting. Any of those signals warrant prompt contact with your prescriber.
If you are already taking both and feel fine, do not panic. Many patients tolerate the combination, especially at modest hawthorn doses of 300 to 900 mg per day of standardized extract. The risk is highest in older adults, those with low baseline blood pressure, and those on multi-drug antihypertensive therapy. Reassess at every clinic visit.
Do not stop metoprolol because you started hawthorn. Abrupt withdrawal of beta-blockers can trigger rebound tachycardia, severe hypertension, or in coronary patients, ischemic events. If you want to taper metoprolol because you feel hawthorn covers the same ground, that decision belongs to your cardiologist.
Tell your prescriber about every herbal product you take, even if you started it months ago. Reviewing all supplements at every cardiology visit catches drift problems before they become clinical events.
Which specific products are affected?
Metoprolol is sold as Lopressor (immediate-release tartrate, twice daily) and Toprol XL (extended-release succinate, once daily) along with generics. The additive hypotensive effect of hawthorn is the same with both formulations.
Hawthorn supplements vary widely. Most clinical research uses standardized extracts like WS 1442 (used in many European trials and sold under brand names such as Crataegutt) or LI 132, dosed at 600 to 1,800 mg per day. Generic capsules and dried herb teas vary in flavonoid content and effect. Combination herbal heart products that mix hawthorn with motherwort, lily of the valley, or arjuna add further uncertainty because those herbs have their own cardiovascular effects.
The interaction concern extends to other beta-blockers including propranolol, atenolol, carvedilol, bisoprolol, and nebivolol, as well as to calcium channel blockers like diltiazem and verapamil. The mechanism, additive blood pressure and heart rate reduction, is class-based rather than metoprolol-specific.
The bottom line
Hawthorn and metoprolol both lower blood pressure and slow heart rate, so combining them stacks their effects in a way that can cause hypotension, bradycardia, dizziness, or falls. The interaction is pharmacodynamic, so timing the doses apart does not help. Discuss any plan to use hawthorn with your cardiologist, monitor blood pressure and pulse closely if you do, and never adjust metoprolol on your own to make room for the herb.