Bioavailability of tramadol hydrochloride after administration via different routes in rats

Tramadol is a synthetic non-opiate analgesic drug and effective for many kinds of chronic and acute pain. This study compared the bioavailability of tramadol after different administration routes in rats (oral, buccal and nasal). A simple HPLC analytical approach was used to determine the concentration of tramadol in plasma. The pharmacokinetic behavior and bioavailability of tramadol after administration via different routes in rats were investigated. Nasal and buccal administration of tramadol resulted in a fast increase followed by a rapid decrease in the plasma tramadol concentration. The Cmax values following buccal and nasal administration were 6 times and 20 times higher than that of oral administration, respectively, (6827.85 ± 7970.87 ng/ml, 22191.84 ± 5364.86 ng/ml, vs 1127.03 ± 778.34 ng/ml). The relative bioavailabilities of the nasal- and buccal-administered drug when compared with the oral route were 504.8% and 183.4%, respectively, which is much higher than that of oral administration. Nasal and buccal administration increased the bioavailability of tramadol, which may allow for a reduction in the dose of tramadol and a subsequent decrease in both side effects and toxicity. Therefore, this approach provides an effective choice for the delivery of tramadol, an analgesic drug.