Garlic: Dosage. Adverse Reactions. Interactions.

2010

Dosage Range

GENERAL GUIDE

• Fresh garlic: 2-5 g/day (ensure it is bruised, crushed or chewed).

• Dried powder: 0.4-1.2 g/day.

• Aged-garlic extracts have been studied in amounts ranging from 2.4 to 7.2 g/day.

• Oil: 2-5 mg/day.

• Garlic preparations that will provide 4-12 mg alliin daily.

• Fluid extract (1:1): 0.5-2 mL three times daily.

ACCORDING TO CLINICAL STUDIES

Hypertension: 600-900 mg/day in divided doses (delivering approximately 5000-6000 µg allicin potential).

• Hyperlipidaemia: 600-9000 mg/day.

• Fungal infection: topical 0.4-0.6% ajoene cream applied twice daily.

• Occlusive arterial disease: 600-800 mg/day.

It is important to be aware of the thiosulfinate content, in particular allicin-releasing ability, of any commercial product to ensure efficacy.

Adverse Reactions

INTERNAL USE

Breath and body odour, allergic reactions, nausea, heartburn, flatulence, abdominal discomfort and diarrhea have been reported.

Headache, myalgia and fatigue were reported in one study using a dose of 900 mg garlic powder (standardised to 1.3% alliin).

TOPICAL USE

An ajoene 0.6% gel produces a transient burning sensation after application, according to one study. Contact dermatitis can occur — one study using patch testing found that 5.2% of volunteers had contact sensitisation.

Significant Interactions

SAQUINAVIR

A clinical study showed that garlic reduces blood levels of saquinavir and therefore may reduce efficacy of drug — avoid using concurrently.

ANTICOAGULANTS

Potentiation effects are possible when using garlic at high doses (>4 g) in excess of usual dietary amounts. Avoid high doses in patients taking anticoagulants unless under professional supervision.

ANTIPLATELET DRUGS

Potentiation effects are possible when using garlic at high doses in excess of usual dietary amounts. Use high doses with caution in patients taking antiplatelet drugs.

ANTIHYPERTENSIVE AGENTS

Theoretically, potentiation effects are possible when using garlic at high doses in excess of usual dietary amounts.

ANTIHYPERUPIDAEMIC AGENTS

Theoretically, potentiation effects are possible when using garlic at high doses in excess of usual dietary amounts however the effect is likely to be minimal — observe.

HEUCOBACTER PYLORI TRIPLE THERAPY

Additive effects are theoretically possible. While it is prudent to observe the patient for adverse reactions, the interaction may be beneficial.

HEPATOTOXIC DRUGS

Garlic may exert hepatoprotective activity against liver damage induced by drugs according to in vitro tests, which suggests a beneficial interaction.

PARACETAMOL

In vivo protection from garlic and ajoene on paracetamol-induced hepatotoxicity has been observed — beneficial interaction.