Diosmin

Diosmin is a flavone glycoside, a member of the flavonoid family of plant compounds, built from the aglycone diosmetin joined to a sugar ^[1]. It occurs naturally in citrus fruit and is manufactured on a large scale from citrus peel, frequently by converting the abundant citrus flavonoid hesperidin into diosmin ^[3]. It belongs to a broad and chemically diverse group of agents known as phlebotonics or venoactive drugs ^[1][2].

Diosmin is used to treat the signs and symptoms of chronic venous disease of the legs, including swelling, heaviness, aching, and, in advanced cases, venous ulcers, as well as the symptoms of hemorrhoids ^[1][2]. It is often given as a micronized purified flavonoid fraction that combines diosmin with hesperidin, a formulation available under names such as Daflon and Detralex ^[3]. In the United States a prescription micronized diosmin product is classified as a medical food rather than a drug ^[3].

The clinical evidence for diosmin and related phlebotonics is modest ^[1]. A Cochrane systematic review found moderate-certainty evidence that these drugs slightly reduce leg swelling and ankle circumference in chronic venous insufficiency, but little or no effect on quality of life and only low-certainty evidence regarding the healing of ulcers ^[1]. For hemorrhoids, a separate Cochrane review reported a potential benefit, with reductions in bleeding and overall symptoms, while cautioning that the underlying trials had methodological limitations ^[2]. Reviews of the micronized formulation have supported its use as generally safe and beneficial, particularly as an adjunct to compression therapy ^[3].

Diosmin is taken by mouth, usually as tablets, and is often supplied in a micronized form intended to improve absorption ^[3]. Its regulatory status varies by country: it is sold as an over-the-counter or prescription medicine in several European nations but is treated as a dietary supplement or medical food in the United States, where regulators have previously judged the evidence insufficient to support general over-the-counter drug use ^[1]. The most commonly reported side effects are mild and mostly involve the digestive tract ^[1].

Diosmin is generally well tolerated; the most common side effects are mild GI upset and occasional headache. It has a long history of use in Europe for venous disease with a good safety record. As always, persistent leg swelling or vein problems should be evaluated by a clinician rather than self-treated indefinitely.

Diosmin is sold as a venous supplement, which tends to obscure the fact that in humans it behaves like a metabolic inhibitor rather than an inert flavonoid.

Three controlled volunteer studies make the point. Ten days of diosmin 500 mg raised fexofenadine peak concentration by 49% and total exposure by 64%, consistent with inhibition of P-glycoprotein efflux. Nine days of the same dose raised metronidazole exposure by roughly a quarter while shifting urinary recovery from metabolites toward unchanged drug. Pretreatment before diclofenac raised its exposure and half-life, pointing at CYP2C9. On that basis diosmin plausibly increases levels of other P-glycoprotein substrates such as digoxin and dabigatran, and of CYP2C9 substrates such as warfarin and phenytoin, where a modest rise in exposure is not trivial.

None of this has been studied at the doses used for chronic venous insufficiency over months, and no clinical outcome data exist; the signal is pharmacokinetic, consistent, and unresolved.

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