Garlic pharmacokinetics

Piscitelli SC, Burstein AH, Welden N, Gallicano KD, Falloon J. The effect of garlic supplements on the pharmacokinetics of saquinavir. Clin Infect Dis 2002 34 234-238. 

Gallicano K, Choudhri S, Leclaire T, Poster BC. Effect of short-term administration of garlic supplements on single-dose ritonavir pharmacokinetics in healthy volunteers. Br J Clin Pharmacol 2003 55 199-202. 

Table 1 Case Reports and Pharmacokinetic Study of Interactions Between Garlic and Prescription Drugs... 

Compared to baseline saquinavir pharmacokinetic parameters obtained in period 1, the use of garlic reduced the mean saquinavir area under the concentration-time curve (AUC) by 51%, and the maximum (Cmax) and minimum (Cmin) saquinavir concentrations by 54% and 49%, respectively. After a 10-day washout, the AUC, Cmax, and Cmin values were within a range of 60% to 70% of baseline values. The magnitude of the decline in concentration might result in therapeutic failure and viral rebound in patients with HIV. Based on the pharmacokinetic parameters obtained in period 3, it also appears that garlic might have a prolonged, albeit lesser, effect on saquinavir exposure. The effects of combined treatment with other protease inhibitors that are also potent cytochrome P-450 (CYP) enzymes modulators need to be further evaluated. 

Animal studies The pharmacokinetic behavior of vinyldithiins, the main constituents of oily preparations of garlic, was investigated after oral administration of 27 mg 1,2-vinyldithiin and 9 mg 1,3-vinyldithiin to rats... 

Lachmann G, Lorenz D, Radeck W, Steiper M. The pharmacokinetics of the S35 labeled garlic constituents alliin, allicin and vinyldithiine. Arzneimittel-forschung 1994 44 734-743. 

Nagae S, Ushijima M, Hatono S, et al. Pharmacokinetics of the garlic compound S-allylcysteine. PlantaMed 1994 60 214-217. 

A garlic supplement reduced the plasma levels of saquinavir by 50% in one study, but had little effect in another. Another garlic supplement did not significantly affect the pharmacokinetics of a single dose of ritonavir. 

Although information is limited, a reduction in saquinavir plasma levels of the magnitude seen in the first study could diminish its antiviral efficacy. All garlic supplements should probably be avoided in those taking saquinavir as the sole protease inhibitor (no longer generally recommended). While the pharmacokinetic effect on single-dose ritonavir was not clinically important, this requires confirmation in a multiple-dose study. 

Garlic dose not affect the pharmacokinetics of alprazolam or dextromethorphan, and is therefore not expected to interact with drugs metabolised by CYP3A4 or CYP2D6. 

In breast cancer patients undergoing treatment with docetaxel (30 mg/m /week), coadministration with 1200 mg garlic daily did not significantly affect docetaxel pharmacokinetics (Cox et al. 2006). 

Chan, K.C., M.C. Yin, and W.J. Chao. 2007. Effect of diallyl trisulfide-rich garlic oil on blood coagulation and plasma activity of anticoagulation factors in rats. Food Chem. Toxicol. 45(3) 502-507. Cox, M.C., J. Low, J. Lee, et al. 2006. Influence of garlic (Allium sativum) on the pharmacokinetics of docetaxel. Clin. Cancer Res. 12(15) 4636-4640. 

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