Squill

Scientific Name(s): Urginea indica (Roxb.) Kunth. (Indian squill), Urginea maritima (L.) Baker (European or white squill), Urginea maritima var. pancratium Stein Baker (red squill)
Common Name(s): European squill, Indian squill, Mediterranean squill, Red squill, Scilla, Sea onion, Sea squill, White squill

Medically reviewed by Drugs.com. Last updated on Feb 20, 2024.

Clinical Overview

Use

Squill is a cardiotonic similar to digitalis but is generally not used medicinally. Traditional uses include as a component of hair tonics to treat seborrhea and dandruff, and as a rodenticide. Clinical studies have evaluated use in alopecia and asthma; however, clinical data are lacking to recommend squill for any indication.

Dosing

Clinical trials are lacking to provide dosing recommendations. Various preparations and formulations exist; strength of squill preparations and extracts may vary. As with any cardiac glycoside-containing product, use squill with caution.

Contraindications

Contraindications have not been identified.

Pregnancy/Lactation

Avoid use. Abortifacient effects and effects on the menstrual cycle have been documented.

Interactions

None well documented.

Adverse Reactions

Adverse reactions include vomiting and convulsions, which generally are observed in overdose situations.

Toxicology

No data.

Scientific Family

• Liliaceae (lily)

Botany

White squill is a perennial herb native to the Mediterranean region. It often grows in sandy soil near the sea, and its onion-like appearance accounts for the common names sea onion or sea squill; a synonym of U. maritima is D. maritima. The bulbous portion of the base is harvested, and the dried inner scales of the bulb (not the central portion of the bulb) is used. White squill has sometimes been adulterated by the inclusion of Indian squill, which has comparable biological activity.(Deb 1976) Red squill is primarily used as a rodenticide.(USDA 2022)

History

Some varieties of squill have been used as rodenticides for more than 1,000 years. Extracts of the bulb were traditionally used as a cardiotonic for the treatment of edema (by the Romans and ancient Egyptians), as an expectorant, and as an emetic. Use as an expectorant in some commercial cold preparations has continued. Because of the popularity of the digitalis glycosides, squill components are rarely used in the United States as cardioactive agents; squill was approved by the German Commission E (revised 1989) for mild cardiac insufficiency and diminished kidney capacity.(Stein 2004) Squill and squill formulations are widely used in Iranian traditional medicine, most commonly for respiratory disorders (ie, pneumonia, chronic bronchitis, asthma).(Nejatbakhsh 2017) Squill has been used traditionally as a cancer remedy.(Duke 1985)

Chemistry

Squill contains a large number of related steroidal cardioactive glycosides. Those found in the greatest concentration in the bulb include scillaren A and proscillaridin A, the aglycone of both being scillarenin. In addition, glucoscillaren A, scillaridin A, and scilliroside have been characterized. In one study, the most common components identified in dried bulbs were scilliroside (approximately 45 ppm) and scillaren A (approximately 38 ppm)(Balbaa 1979); other studies have found proscillaridin A in the greatest concentration.(Garcia Casado 1977) Scillaren B refers to a mixture of squill glycosides.(Leung 1980) Components of squill tissue cultures appear to vary in quantitative composition from whole bulb extracts.(Shyr 1976) Furthermore, extracts from fresh bulbs can vary based on the time of year they are collected. Many novel cardiac glycosides have been isolated and identified from squill.(Iizuka 2001, Kopp1996, Krenn 1996, Krenn 2000) Indian squill also contains proscillaridin A and scillaren A as major glycosides, with minor components differing from white squill.(Jha 1981) Glycosides of red squill also have been studied.(Balbaa 1979, Verbiscar 1986) Other constituents found in squill include flavonoids,(Fernandez 1972, Fernandez 1975) the fructan sinistrin,(Spies 1992) and related carbohydrates(Praznik 1993) and an antifungal glycoprotein.(Deepak 2003)

Uses and Pharmacology

Methanolic extracts of red squill have been used as hair tonics in treating seborrhea and dandruff, the activity being ascribed to scilliroside.(Leung 1980)

In general, red squill is not used medicinally; the powdered dried bulbs of red squill are mainly used as rodenticides. Death is caused by the centrally induced convulsant action of scilliroside, rather than by direct cardiotoxicity. Rats lack a vomit reflex and are insensitive to the emetic action of these glycosides. Because squill-laced bait is vomited by domestic animals before a lethal dose can be absorbed, often it is considered to be a rat-specific agent.(Balbaa 1979)

Alopecia

Clinical data

A double-blind, randomized study compared the effects of white squill (U. maritima) 2% and clobetasol propionate 0.05% lotions in 42 patients in Iran who presented to the hospital with alopecia areata. Patients (72% male) were at least 6 years of age (mean age, 29 years; range, 9 to 52 years) with scalp alopecia and at least 25% scalp hair loss. Squill or clobetasol lotion was topically applied twice daily for 12 weeks. Compared with clobetasol, squill significantly increased overall hair regrowth scores by month 2 of treatment (P=0.000); by month 3, the percentage of patients experiencing more than 75% growth was significantly greater in the squill group (23.3% vs 9.6%; P<0.05). Rate of mean hair growth and vellus hair growth, as well as mean size of the affected areas and satisfaction rates, were similar between groups at month 3.(Moosavi 2020)

Arthritis

Animal data

Rheumatoid arthritis and inflammatory paw edema were attenuated by U. indica ethanolic and aqueous extracts (3% and 3.5%, respectively) in a variety of acute and chronic inflammation rat models. At day 23, reduction in arthritic development by the extracts and the positive control, piroxicam, were significant compared with controls, with the ethanolic extract performing similar to piroxicam (P<0.001 for all 3 treatments). Similar significant results were observed for suppression of paw edema.(Akhtar 2019)

Asthma

Animal data

Studies in rat tissues indicate a bronchodilatory effect of U. maritima extract via beta-2 receptor stimulation, muscarinic receptor inhibition, calcium channel blocking, and potassium channel opening mechanisms. Effects of the extract were comparable with that of theophylline.(Kazemi Rad 2021)

Clinical data

In a triple-blind, randomized, placebo-controlled trial, effects of adjunctive squill vinegar syrup (Squill Oxymel) use was investigated in adult Iranian patients with moderate to severe persistent asthma (forced expiratory volume in the first second of expiration [FEV₁] less than 80% predicted) (N=60). Squill vinegar syrup, simple vinegar syrup, or placebo was consumed at a dose of 10 mL twice daily for 6 weeks as add-on to routine treatment (ie, for at least the past 6 months) with high-dose combination inhaled corticosteroids (fluticasone or budesonide) and long-acting beta-agonists. Significant improvement was observed with squill vinegar syrup in multiple spirometry parameters (ie, FEV₁, percent FEV₁, percent FEV₁/forced vital capacity [FVC]) compared with the other 2 groups, while both the squill vinegar syrup and simple vinegar syrup resulted in higher respiratory questionnaire scores than placebo (P<0.001 for both). No significant differences in plethysmography parameters were observed among groups. Mild nausea and vomiting were reported in the squill vinegar syrup and simple vinegar syrup groups (n=2 and n=3, respectively).(Nejatbakhsh 2017)

Cancer

In vitro data

An in vitro study showed that proscillaridin A, a cardiac glycoside constituent of U. maritima, inhibited proliferation and induced apoptosis in prostate cancer cells in a dose-dependent manner; furthermore, proscillaridin A inhibited Jak2/STAT3 signalling and augmented doxorubicin toxicity.(He 2018)

Cardiovascular effects

Squill glycosides have cardiotonic properties similar to digitalis. However, squill components are generally poorly absorbed from the GI tract and are less potent than digitalis.(Duke 1985)

Animal and in vitro data

Animal and in vitro studies evaluating white squill extract have demonstrated positive inotropic effects (in isolated rabbit atrium) but also negative chronotropic effects (in experimental rats).(Dizaye 2010) Squill extracts caused peripheral vasodilation and bradycardia in anesthetized rabbits.(Shyr 1976)

Dyspareunia

Clinical data

In a triple-blind, randomized, 2-group controlled trial in postmenopausal women (N=60), an oil extract of squill used topically 2 to 3 times weekly for 4 weeks decreased dyspareunia compared with placebo (olive oil); however, the study had multiple limitations.(Karimi 2021)

Dosing

Clinical trials are lacking to provide dosing recommendations.

Various squill preparations and formulations exist; strength of preparations and extracts may vary. As with any cardiac glycoside-containing product, use squill with caution.

Squill vinegar syrup at a dosage of 10 mL twice daily for 6 weeks (as add-on to routine asthma treatment) was evaluated in a small study of patients with stable moderate to severe persistent asthma.(Nejatbakhsh 2017)

Preparations for oral administration are enteric coated to prevent degradation by gastric acid. Meproscillaren, a semisynthetic derivative of proscillaridin, is absorbed orally and may be effective in certain individuals.(Bayazit 2010)

Pregnancy / Lactation

Avoid use. Abortifacient effects and effects on the menstrual cycle have been documented.(Newall 1996)

Interactions

Use caution when coadministered with calcium, laxatives, quinidine, saluretics, and extended glucocorticoid therapy.

Adverse Reactions

Adverse reactions related to squill include vomiting and convulsions, which generally are observed in overdose situations. In general, red squill is not used medicinally and may induce convulsions.

A pilot study on the effect of squill in asthma reported mild nausea and vomiting among some participants.(Nejatbakhsh 2017)

Toxicology

Although white squill and its extracts have the potential to induce life-threatening cardiac effects in relatively low doses, they generally have not been associated with human toxicity. Vomiting often is induced as a reflex in cases of overdosage, minimizing the absorbed dose. The toxic dose of squill soft mass (a galenical extract form used to make certain squill preparations) in guinea pigs is 270 mg/kg; tinctures made from Indian squill caused death at a dose of 36 mg/kg.(Hakim 1976a, Hakim 1976b) Fresh bulbs contain a vesicant.(Duke 1985)

Index Terms

• Drimia maritima

References

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