Preparation and evaluation of a novel delayed-onset sustained-release system of propranolol hydrochloride.

The objective of this work was to prepare and evaluate a new delayed-onset sustained-release system, comprising a sustained-release core tablet with hydroxypropyl methylcellulose as polymer matrix and an ethylcellulose/Eudragit L coating capable of delaying the drug release. The sustained core containing propranolol hydrochloride as the model drug was prepared by granulate tableting and the polymer coating was applied in a computer-controlled coating pan. The dissolution tests demonstrated that the in-vitro drug release was pH-dependent with sufficient gastric resistance, and the lag time (t(10%)) could be controlled by adjusting the coating level. Three dosage forms including commercial tablet, sustained-release tablet and the delayed-onset sustained-release tablet were administrated to six beagle dogs and the plasma levels of propranolol hydrochloride were measured with high-performance liquid chromatography. The delayed-onset sustained-release tablet had a lag time of 3.0 h in-vitro and 3.5 h in-vivo, and a t(max) of 7.0 h. The relative bioavailability for delayed-onset sustained-release tablet was 96.98% compared with commercial tablets. The results indicate that the new propranolol delayed-onset sustained-release system could achieve a relatively constant drug release followed by a programmed lag time, and this may provide a promising drug delivery form for chronopharmacotherapy of certain cardiovascular diseases.

[Introduction of Plasmodium falciparum C-terminal region of the merozoite surface protein gene into the chloroplast of tobacco].

OBJECTIVE: To construct chloroplast expression vector, and introduce the C-terminal region of the merozoite surface protein 1 gene (msp1-42) of Plasmodium falciparum 3D7 strain into the chloroplast genome of tobacco for expression of the recombinant protein MSP1-42. METHODS: Forward and reverse primers, adjusted to tobacco chloroplast codon preferences, were used for generation of msp1-42 gene from pBluntmsp plasmid which contains msp1-42 gene. A chloroplast expression vector LRrrmsp was constructed and bombarded into leaves of tobacco by a biolistic He particle delivery system. Media containing 500 mg/L spectinomycin were used for selection of spectinomycin resistant plant. PCR was carried out to check the introduction of the msp1-42 and aadA genes into the chloroplast genome. The transgenic plants with msp1-42 and aadA gene insertion were cut and cultured on the generation MS media containing 500 mg/L spectinomycin for at least 3 turns, and multiple PCR were applied to analyse their homogenization. RESULTS: A chloroplast expression vector LRrrmsp was constructed and confirmed with PCR and enzyme digestion analysis. Six transformants were obtained with a transformation rate 0.6/gun. The msp1-42 and aadA genes were amplified from spectinomycin resistant plants by PCR detection. Wild type chloroplast gene was detected by multiple-PCR analysis. CONCLUSION: A chloroplast expression vector containing msp1-42 gene was constructed. The msp1-42 gene was introduced into chloroplast genome of tobacco and heterogeneous transgenic tobacco was obtained.

[An experimental serum pharmacological study on an application method in traditional Chinese medicine for treatment and prevention of asthma].

OBJECTIVE: To study the mechanism of herbal application along meridians for treatment and prevention of asthma by using serum pharmacological test to observe the effects of serum containing herbs against the constriction of tracheal spiral strips induced by acetylcholine chloride (Ach). METHODS: Guinea pigs were randomly divided into normal control group, normal saline (NS) application group, aminophylline application group, aminophylline injection group, 1-day herb application group, 7-day herb application group and 14-day herb application group. Asthma was induced by Hutson's method in guinea pigs except the normal control group. Guinea pigs in herb application groups were treated by external application of a compound herbal medicine 60 min once every day. Guinea pigs in NS application group were treated by external application of NS. Guinea pigs in the two aminophylline-treated groups were treated by external application and intraperitoneal injection of aminophylline at a dose of 400 mg/kg, respectively. The guinea pigs were killed and the sera were obtained after 1-day, 7-day and 14-day treatment in the three herb application groups, 7-day treatment in the NS application group, the aminophylline application and injection groups, respectively. Serum pharmacological method was used to do the experiment, the effects of different sera on the constriction of tracheal strips were observed, and the constriction rates were calculated. RESULT: The serum containing herbs had an effect in reducing the constriction of tracheal spiral strips induced by Ach, and the effect was similar to that of the serum obtained from the aminophylline injection group. The constriction rate of the tracheal spiral strips was decreased when herbal application treatment was prolonged within a period of time, and it became stable when herbal application treatment was between 7-14 days. The constriction of tracheal spiral strips induced by Ach could be reduced remarkably when it was previously treated by serum containing herbs. CONCLUSION: The anti-acetylcholine function with a time-dependent effect is one of the mechanisms of herbal application treatment along meridians for asthma, and furthermore, herbal application treatment along meridians might be useful for preventing asthma.