Increased sensitivity to diltiazem hypotensive effect in an experimental model of high-renin hypertension

Pharmacokinetic-Pharmacodynamic Modeling to Study the Antipyretic Effect of Qingkailing Injection on Pyrexia Model Rats

Qingkailing injection (QKLI) is a modern Chinese medicine preparation derived from a well-known classical formulation, An-Gong-Niu-Huang Wan. Although the clinical efficacy of QKLI has been well defined, its severe adverse drug reactions (ADRs) were extensively increased. Through thorough attempts to reduce ADR rates, it was realized that the effect-based rational use plays the key role in clinical practices. Hence, the pharmacokinetic-pharmacodynamic (PK-PD) model was introduced in the present study, aiming to link the pharmacokinetic profiles with the therapeutic outcomes of QKLI, and subsequently to provide valuable guidelines for the rational use of QKLI in clinical settings. The PK properties of the six dominant ingredients in QKLI were compared between the normal treated group (NTG) and the pyrexia model group (MTG). Rectal temperatures were measured in parallel with blood sampling for NTG, MTG, model control group (MCG), and normal control group (NCG). Baicalin and geniposide exhibited appropriate PK parameters, and were selected as the PK markers to map the antipyretic effect of QKLI. Then, a PK-PD model was constructed upon the bacalin and geniposide plasma concentrations vs. the rectal temperature variation values, by a two-compartment PK model with a Sigmoid Emax PD model to explain the time delay between the drug plasma concentration of PK markers and the antipyretic effect after a single dose administration of QKLI. The findings obtained would provide fundamental information to propose a more reasonable dosage regimen and improve the level of individualized drug therapy in clinical settings.

Diltiazem reduces mortality and breakdown of ATP in red blood cell induced by isoproterenol in a freely moving rat model in vivo

The benefit of calcium channel blockers for cardiovascular prevention against heart attack and stroke has not been firmly supported. We investigated the possible cardiovascular protective effect of diltiazem (DTZ) against injury induced by isoproterenol using a freely moving rat model in vivo. Sprague Dawley rats were injected subcutaneously (sc) with either 5 or 10 mg/kg of DTZ, or saline as control, twice daily for five doses. One hour after the last injection, a single dose of isoproterenol (30 mg/kg) was injected sc to each rat. Blood samples were collected serially for 6 h for measurement of adenine nucleotides (ATP, ADP and AMP) in red blood cell (RBC) by a validated HPLC. The study has shown isoproterenol induced 50% mortality and also increased RBC concentrations of AMP from 0.04 ± 0.02 to 0.29 ± 0.21 mM at the end of the experiment (p < 0.05). Treatment with 10 mg/kg of DTZ reduced mortality from 50% to <20% and attenuated the increase of RBC concentrations of AMP from +0.25 ± 0.22 in the control rats to +0.072 ± 0.092 mM (p < 0.05). The study concluded that 10 mg/kg of DTZ reduced mortality and breakdown of ATP induced by isoproterenol in rats.

Pharmacokinetics of diltiazem hydrochloride delay-onset sustained-release pellet capsules in healthy volunteers

The pharmacokinetics (PK) of ordinary tablets and sustained release capsules of diltiazem hydrochloride in human clinical trials had been studied. The PK of diltiazem hydrochloride delay-onset sustained-release pellet capsules, a new dosage form, has not been reported, although it is very important to clinical use. In this paper, we investigated the PK of diltiazem hydrochloride delay-onset sustained-release pellet capsules and the food influence in Chinese healthy volunteers. The PK parameters indicated that the diltiazem hydrochloride delay-onset sustained-release pellet capsules appeared marked characteristics of delayed and controlled release. An opened-label, randomized and parallel clinical trial was conducted in 36 Chinese healthy volunteers with single oral dose (90 mg, 180 mg or 270 mg) and a multiple oral dose (90 mg d-1×6 d) administration. The effect of food on the PK of one single oral dose (360 mg) was investigated in 24 healthy Chinese volunteers. Plasma diltiazem concentration was determined by reversed-phase high-performance liquid chromatography (RP-HPLC) and the main pharmacokinetic parameters were analyzed by PKSolver (Ver 2.0). All clinical studies were conducted in the Clinical Pharmacological Center (No. JDX1999064) of Xiangya Hospital Affiliated Central South University, China. The PK parameters suggested that the new formulation had marked characteristics of delayed and controlled release of diltiazem, and food intake did not alter significantly diltiazem pharmacokinetic parameters.

Comparing pharmacokinetics and metabolism of diltiazem in normotensive Sprague Dawley and Wistar Kyoto rats vs. spontaneously hypertensive rats in vivo

BACKGROUND

In order to identify a suitable rodent model for preclinical study of calcium antagonists, the pharmacokinetics and metabolism of one of the prototypes diltiazem (DTZ) in normotensive Sprague Dawley (SDR) was compared with Wistar Kyoto (WKY) rats and spontaneously hypertensive rats (SHR) following 5 mg/kg twice daily for five doses given by subcutaneous injection.

METHODS

Pharmacokinetic data were analyzed by standard procedures assuming a one-compartment model with first-order input using Rstrips(®), and differences between the groups were considered significant when p<0.05.

RESULTS

Plasma concentrations of DTZ were higher in the SHR than the normotensive SDR and WKY rats, although the differences did not reach statistical significance (p>0.05). Plasma concentrations of the active metabolites N-desmethyl DTZ (MA), deacetyl DTZ (M1) and deacetyl N-desmethyl DTZ (M2) were significantly higher in the SHR and WKY rats than the SDR, which was attributed to higher DTZ concentrations and also genetic factors.

CONCLUSIONS

Although the differences were mainly quantitative and very small, the study has shown for the first time that the metabolism profiles of DTZ in SHR and WKY rats were closer to humans than SDR, and they may be more preferable rat models to study pharmacokinetic and metabolism studies of DTZ or similar agents.