Pharmacokinetic evaluation of guar gum-based colon-targeted oral drug delivery systems of metronidazole in healthy volunteers

Metronidazole Based Floating Bioadhesive Drug Delivery System for Potential Eradication of H. pylori: Preparation and In Vitro Characterization

Metronidazole has the potential to produce local stomach specific action in order to treat Helicobacter pylori induced peptic ulcer disease. The current project executes the development of osmotically controlled bioadhesive metronidazole loaded effervescent floating tablets with optimized floating and swelling behavior. Direct compression technique was used to prepare the tablets. The designed formulations exhibited physico-chemical properties within acceptable optimum limits as per pharmacopeial requirements. The results of tablet floating studies revealed that all formulations, except F1 and F5, had good buoyancy characteristics (TFT > 12 h except F2 and F8 with TFT of 6 h). Formulation F2 containing guar gum in higher concentration with carbopol and formulation F8 containing guar gum in 50% decreased concentration in combination with HPMC and carbopol had enhanced FLT appreciably, with least TFT as compared to formulations F3, F4, and F6 (ANOVA; p ≤ 0.05). Formulation batches of F3, F4, and F6 exhibited appreciable FLT as well as TFT and were optimized formulations. Out of the above mentioned optimized batches, F4 and F6 formulations showed low FLT (4 and 5 s respectively). The results of the swelling study indicated a proportionate increase in the swelling index with increase in time. A significantly higher swelling ratio was found with formulation F6 and F4 compared with that of F7 and F8 (ANOVA; p ≤ 0.05). Additionally, the impact of pH change, agitational intensity, as well as increasing concentration of NaCl was investigated on drug release. It was observed that agitational intensity had no effect on drug release rate while increasing concentration of NaCl produced an increased drug release from the dosage form as compared to the drug release exhibited by the formulations in the absence of NaCl. Overall, this project could have valuable contribution in the fabrication of metronidazole loaded effervescent floating tablets. Gastro-retentive systems are expected to enhance local stomach specific action of anti H. pylori agents based on their buoyancy and swelling behavior.

Preparation of Colon-Targeted Acetylharpagide Tablets and its Release Properties in vivo and in vitro

Ethno Pharmacological Relevance: Acetylharpagide is a monomeric compound extracted from Ajuga decumbens, widely used for remedying infectious and inflammatory diseases in Southern China.

Aim of the Study: The present study designed and investigated the formulation of colon-targeted acetylharpagide tablets according to the dual controlled release mechanisms of time-delay and pH-sensitivity.

Materials and Methods: The core tablets of acetylharpagide were coated with the material used in time-delay systems such as ethyl cellulose and suitable channeling agent, followed by pH-dependent polymers, polyacrylic resin II and III in a combination of 1:4. Furthermore, the release and absorption performance of colon-targets tables were evaluated in vitro and in vivo. In the in vitro tests, the optimized formulation was not released in simulated gastric fluid in 2 h; the release was <5% at pH 6.8 simulated intestinal fluids for 4 h; the drug was completely released within 5 h at pH 7.6 simulated colon fluid. In the in vivo tests, pharmacokinetic characteristics of the colon-targeted tablets were investigated in dogs.

Results: The results indicated that the acetylharpagide tablets with the technology of colon-targeting caused delayed T_max, prolonged absorption time, lower C_max, and AUCINF_obs. Meanwhile, the apparent volume of distribution (Vz_F_bs) of the colon-target tablets was higher than the reference.

Conclusions: These results suggested that colon-targeted acetylharpagide tablets deliver the drug to the colon. The in vitro performance of colon-targeted acetylharpagide tablet was appropriately correlated with its performance in vivo.

Colonic treatments and targets: issues and opportunities

The colon provides a plethora of therapeutic opportunities. There are multiple disease targets, drug molecules, and colon-specific delivery systems to be explored. Clinical studies highlight the potential for systemic delivery via the colon, and the emerging data on the levels of cell membrane transporters and metabolic enzymes along the gut could prove advantageous for this. Often efflux transporters and metabolic enzyme levels are lower in the colon, suggesting a potential for improved bioavailability of drug substrates at this site. The locoregional distribution of multiple metabolic enzymes (including cytochromes), efflux transporters (including P-glycoprotein and breast cancer resistance proteins), and influx transporters (including the solute carrier family) along the intestine is summarized. Local delivery to the colonic mucosa remains a valuable therapeutic option. New therapies that target inflammatory mediators could improve the treatment of inflammatory bowel disease, and old and new anticancer molecules could, when delivered topically, prove to be beneficial adjuncts to the current systemic or surgical treatments. New issues such as pharmacogenomics, chronotherapeutics, and the delivery of prebiotics and probiotics are also discussed in this review. Targeting drugs to the colon utilizes various strategies, each with their advantages and flaws. The most promising systems are considered in the light of the physiological data which influence their in vivo behavior.

Hydrotherapy as a possible neuroleptic and sedative treatment

Psychotic symptoms such as delusions and hallucinations can have a devastating effect on a patient's social functioning. Since psychosis is rarely congenital, it is possible that lifestyle factors play a role in its etiology. This paper offers a hypothesis that some of these factors could be: (a) A lifestyle lacking evolutionarily conserved stressors such as frequent exposure to heat and/or cold, resulting in a lack of "thermal exercise" which could lead to malfunctioning of the brain. (b) Partial retention and absorption of toxic waste in the colon, as described in more detail below. (c) Genetic makeup that makes a person vulnerable to the above conditions. To test the hypothesis, three types of hydrotherapy are proposed (to be tested separately) as a putative neuroleptic treatment: head-out hot showers, adapted cold showers (twice daily each), and colon hydrotherapy (every 3-12 weeks, which also includes a dietary change according to Harvard's Healthy Eating Pyramid). The following is supporting evidence: Dopaminergic transmission in the mesolimbic pathway is involved in central processing of pain and negative stimuli (e.g. stress-induced analgesia) in addition to its role in the pathophysiology of psychosis. It is also known that if a neural pathway can perform two different functions, then the execution of one function will often suppress the other (e.g. gate control theory of pain). Thus, a pain-based therapy, such as a moderately hot shower, could have a "crowding out" effect on pathological processes within the mesolimbic system. In addition, hyperthermia is known to induce fatigue and depress activity of the frontal cortex (the sedative effect). As described previously, an adapted cold shower could work as a mild electroshock applied to the sensory cortex and, therefore, it might have an antipsychotic effect similar to that of electroconvulsive therapy. Additionally, a cold shower is a vivid example of stress-induced analgesia and would also be expected to "crowd out" or suppress psychosis-related neurotransmission within the mesolimbic system. Human and bacterial toxic waste can sometimes be partially retained in the colon and it is known that many high-molecular-weight compounds can be absorbed there. Most narcotics can cause intoxication if administered rectally and there is also significant comorbidity of schizophrenia with intestinal illnesses. Additionally, there is indirect evidence that colon cleansing can significantly improve mental state. Therefore, it is possible that chronic intoxication with yet unknown components of partially retained waste could be one of the unrecognized organic causes of psychosis.

Novel drug delivery strategies for the treatment of inflammatory bowel disease

Inflammatory bowel disease (IBD) encompasses two idiopathic inflammatory diseases of the intestinal tract: Crohn's disease and ulcerative colitis. Existing therapy for IBD consists mainly of orally or rectally administered small drug molecules, such as 5-aminosalicylates and corticosteroids, or potent systemic immune suppressants. IBD presents a challenging target for drug delivery, particularly by the oral route, as, contrary to most therapeutic regimens, minimal systemic absorption and maximal intestinal wall drug levels are desired. Several delivery strategies are employed to achieve this goal, including the chemical modification of the drug molecules, the use of controlled- and delayed-release formulations and the use of bioadhesive particles. The goal of this review is to summarise existing IBD therapy and examine novel approaches in intestinal drug delivery.