Background: Millions of people today use herbs either as food or in the form of medicine
along with other medications. Many of the herbs can interact with these medications, causing either
potentially dangerous side effects or improved or reduced benefits from the medication.
Objective: The present study was performed to determine the influence of cinnamon, on the
pharmacokinetics and pharmacodynamics of pioglitazone.
Method: Studies were conducted in normal and alloxan induced diabetic rats and rabbits with oral
administration of selected doses of pioglitazone, cinnamon and their combination. Blood samples
were collected at regular intervals of time and were analysed for glucose by GOD/POD method and
for pioglitazone by HPLC method respectively. Body weights were also measured every week.
Results: Significant differences were seen in pharmacokinetic parameters of pioglitazone like AUC,
t1/2, Ke, Cl/F, Vd/F when given in combination with cinnamon in normal and diabetic rabbits. The
combination of pioglitazone and cinnamon was found to reduce the glucose levels and body weights
significantly than pioglitazone. The results indicating increased AUC of pioglitazone on pretreatment
with cinnamon suggest an interaction indicating decreased metabolism of pioglitazone as a
result of CYP 3A4 inhibition and thereby producing a potentiating effect.
Conclusion: Cinnamon enhanced the bioavailability of pioglitazone by inhibiting the CYP3A4
enzyme. Hence, cinnamon might be beneficial when used in combination with pioglitazone in
diabetic patients and an adjustment of dose of pioglitazone may be necessary.