Hawthorn: Dosage. Interactions. Practice Points
• Infusion of dried herb: 0.2-2 g three times daily.
• Tincture of leaf (1:5): 3.5-17.5 mL/day.
• Fluid extract (1:2): 3-6 mL/day.
• Herpes simplex outbreak: 4 mL three times daily at the first sign of infection for a maximum of 2 days.
No target toxicity to 100-fold the human dose of the WS 1442 extract is defined. This is in contrast to inotropic drugs, such as digoxin, which generally have a low therapeutic index.
Sweating, nausea, fatigue and a rash on the hands have been reported in one clinical trial using a commercial preparation containing 30 mg hawthorn extract standardised to 1 mg procyanidins. Headache, sweating, dizziness, palpitations, sleepiness, agitation, and gastrointestinal symptoms have also been reported.
Controlled studies are not available; therefore, interactions are based on evidence of activity and are largely theoretical and speculative.
Hawthorn may theoretically potentiate the effects of cardiac glycosides, as both in vitro and in vivo studies indicate that it has positive inotropic activity. Furthermore, the flavonoid components of hawthorn may also affect P-glycoprotein function and cause interactions with drugs that are P-glycoprotein substrates, such as digoxin. In practice, however, a randomised crossover trial with eight healthy volunteers evaluating digoxin 0.25 mg alone for 10 days and digoxin 0.25 mg with Crataegus special extract WS 1442 (hawthorn leaves with flowers) 450 mg twice daily for 21 days found no significant difference to any measured pharmacokinetic parameters, suggesting that hawthorn and digoxin in these doses may be co-administered safely. Caution — use under professional supervision and monitor drug requirements.
Theoretically, hawthorn may potentiate blood pressure-lowering effects, thereby requiring modified drug doses. Observe patients taking this combination and monitor drug requirements — interaction may be beneficial under professional supervision.
In vivo and in vitro evidence of uterine activity has been reported, therefore this herb should not be used in pregnancy.
Practice Points / Patient Counselling
• Hawthorn has positive inotropic action, increases coronary blood flow, reduces myocardial oxygen demand, protects against myocardial damage, improves heart rate variability, as well as having hypotensiveand antiarrhythmic effects.
• Although considered relatively effective, heart disease can be a very serious medical condition with a rapidly changing course and should not be treated without close medical supervision. In particular, chest pain and shortness of breath are extremely serious symptoms that require immediate medical attention.
• It may take 2-6 weeks’ treatment to notice a benefit of treatment with hawthorn, and heart rate and blood pressure should be monitored.
• Hawthorn also exhibits antioxidant, anti-inflammatory, antiviral and lipid-lowering activity.
• Great care should be exercised if hawthorn is to be combined with other drugs that affect the heart.
Answers to Patients’ Frequently Asked Questions
What will this herb do for me?
Hawthorn appears to be useful in treating a variety of heart conditions such as high blood pressure, hyperlipidaemia and heart failure.
When will it start to work?
Studies suggest it will start to have effects in 2-6 weeks.
Are there any safety issues?
Heart conditions are potentially serious, therefore professional supervision is required.