NIPRD-AH1 is being developed from freeze-dried aqueous extract of Andrographis paniculata at the National Institute for Pharmaceutical Research and Development (NIPRD), Abuja Nigeria as immunestimulant for HIV infected patients. The aim of this study was to evaluate the effect of NIPRD-AH1 on human cytochrome P450 3A4 (CYP3A4) drug metabolising enzyme in order to generate clinically significant data for its safe and efficacious use. Activity on CYP3A4 was measured with and without the addition of NIPRD-AH1 in a reaction medium with testosterone (70 μM) as CYP3A4 substrate, and ketoconazole (2.5 μM) as positive inhibitor. The metabolites formed after the enzymatic reactions were quantified by validated HPLC techniques. Results showed NIPRD-AH1 exhibiting low IC50 value of 0.03 mg/ml, indicating that its metabolic processes are likely to inhibit CYP3A4. This suggests possibility of herb-drug interaction, with potential implication on concomitant administration of NIPRD-AH1 with CYP3A4 substrates. We therefore suggested that this effect be examined in vivo in order to draw a definitive conclusion.Keywords: Andrographis paniculata, NIPRD-AH1, CYP3A4, herb-drug interaction.