Table 1.

Relevant herb-drug interactions with commonly prescribed antidiabetic drugs [Holstein et al., 2012, Rehman et al., 2014].

Interacting herb	Pharmacokinetic mechanism; pharmacodynamic mechanism	Antidiabetic drug affected
Aloe vera	inhibitory effects on CYP3A4 and CYP2D6; insulin-sensitizing effects	increased efficacy: Pioglitazone and Repaglinide; additive effects with antidiabetics in general
Andrographis paniculata	inhibitory effects on CYP3A4 and CYP2C9 activities; enhanced glucose transport by glucose transporter 4	probably increased efficacy: Glibenclamide, Glimepiride, Nateglinide, Rosiglitazone; Pioglitazone, and Repaglinide; maybe additive effects with antidiabetics in general
Ginseng	induction of CYP3A4; stimulates insulin secretion	probably decreased efficacy: Glibenclamide; Pioglitazone; Meglitinides; Sitagliptin, Saxagliptin; additive effects with antidiabetics
Karela (Momordica charantia)	inhibition of CYP2C9; stimulates insulin secretion	probably increased efficacy: Glibenclamide, glimepiride, nateglinide, and Rosiglitazone; additive effects with antidiabetics in general
Lycium	inhibition of CYP2C9; improved glucose transport and insulin signaling	slightly increased efficacy (maybe): Glibenclamide, Glimepiride, Nateglinide, and Rosiglitazone; maybe additive effects with antidiabetics in general
St John’s Wort	induction of CYP3A4, 1A2, 2D6, 2E1; drug transporter: p-glycoprotein induced	decreased efficacy. Sulfonylurea; Thiazolidinediones; Meglitinides; Sitagliptin (probably), Saxagliptin (probably)
Herbs with Glucosamines	increased insulin resistance	may diminish antidiabetic efficacy
Herbs with Isoflavones	inhibitory effects on CYP2C9 and CYP3A4	probably increased efficacy: Glibenclamide, Glimepiride, Nateglinide, Rosiglitazone; Pioglitazone, and Repaglinide
Herbs with Levocarnitine	increased glucose oxidation	additive effects with antidiabetics in general