The design, performance and evaluation of bioavailability and bioequivalence have evolved over the last two decades. Bioequivalence (BE) means the absence of a greater-than-allowable difference between the systemic bioavailability of a test product and that of a reference product. Due to efforts by academia, the pharmaceutical industry and health authorities, there is far-reaching consensus on essential questions of bioequivalence trials which have been reflected in the many regulatory guidelines. Despite the introduction and wide acceptance of stringent requirements for bioequivalence studies, there is, however, increasing awareness that some fundamentals of bioequivalence assessment need to be reconsidered in principal. This includes several debatable issues such as practical strategies for bioequivalence of highly variable drugs, drugs with long half life, drugs under genetic polymorphic metabolism, biopharmaceuticals and endogenous substances; single bioequivalence range for all drugs; inclusion of female volunteers; individual versus average bioequivalence; metrics of absorption; etc. This article is an attempt to highlight current thinking on issues in bioequivalence.

Objective: Isolation of the total saponins from Acanthophyllum squarrosum Boiss. and investigation of its surface activity, haemolytic effects on human erythrocytes, as well as enhancing potentials on intranasal insulin absorption in rat as compared to two other enhancers, i.e, Quillaja total saponin (QTS) and sodium cholate (SC). Materials and Methods: The decrease in blood glucose levels in five fasting rats following nasal administration of regular insulin solutions in the presence or absence of enhancers was determined by glucometric strips and used as an indication of insulin absorption. Results: The results showed that Acanthophyllum total saponin (ATS) decreased surface tension of water to about 50 dyne/cm and caused complete haemolysis of human RBCs at a concentration of 250 µg/ml. Following the instillation of solutions containing insulin and different absorption enhancers into the right nostril of rats, the percentage decrease in initial blood glucose was as follows: 72.46% (±2.39%) for ATS, 63.22% (±11.06%) for QTS and 60.06% (±14.93%) for SC. Percentage lowering of initial blood glucose concentrations against time showed that ATS exerts a stronger effect than the two other enhancers, although the difference was not statistically significant (P > 0.05). Conclusion: ATS has a considerable absorption enhancing effect and can possibly be used to increase insulin bioavailability via the nasal route. However, the potential toxic effects of this saponin on nasal mucosa should be further evaluated.

In this study, Trans-01, a polyherbal formulation, was explored for its antidepressant properties, using the forced swim test (FST), tail suspension test (TST) and forced swimming stress (FSS)-induced alterations in serum corticosterone levels. For this purpose, the effect different doses of Trans-01 (25, 50, 75 and 100 mg/kg; PO) were studied. Trans-01 was found to safe up to a dose of 5000 mg/kg since no mortality was observed within 48 h of administration. In TST, Trans-01 showed a dose-dependent decrease in immobility time, which is an indication of its antidepressant effect; this finding was further reinforced in the FST, where a significant effect on immobility was witnessed. However, to explore the possible mechanism of action of Trans-01, the FSS was used to induce corticosterone levels; Trans-01 significantly attenuated the elevated corticosteroid levels. A locomotor activity test was carried out to ascertain whether the antidepressant effect of Trans-01 included general body stimulation. These results indicate that Trans-01 can be a potential candidate for managing depression. However further studies are required to substantiate the same which are underway in our lab.

Parkinson's disease (PD) is a neurodegenerative disease in the nigrostriatal pathway of animals and humans and is responsible for most of the movement disorders, including the rigidity. Increasing evidence suggests that an inflammatory reaction accompanies the pathological processes caused by cyclooxygenase-2 (COX-2) seen in many neurodegenerative disorders, including PD. In this study oral betamethasone and dexamethasone were administrated to parkinsonian rats chronically and their effect on rigidity was evaluated. As the results of this study show, both the molecules were able to decrease rigidity.

Aim: Euphorbia prostrata (Euphorbiaceae) is traditionally used in Cameroon for the treatment of many diseases, including diarrhea. We investigated the acute toxicity and effect of the aqueous ethanol extract of the plant on gastrointestinal propulsion, in vitro bacterial growth and in vivo bacillary dysentery. Materials and Methods: Diarrhea was induced by oral administration of 12 x 10 ⁸ Shigella dysenteriae type 1 (Sd1) cells. Diarrheic rats were treated for 5 days with 10, 20 or 40 mg/kg extract or 20 mg/kg norfloxacin. The faeces frequencies and the number of Sd1 were assessed and the death rate recorded. Results: The aqueous ethanol extract of E. prostrata was not toxic. In vitro, the minimal inhibitory and minimal bactericidal concentrations of the extract were 3,500 and 12,000 µg/ml, respectively. In vivo, diarrhea went along with increase in faeces frequency (P < 0.01 by the 3 ^rd day), increase in the bacterial population to a maximum on the 2 ^nd day after infection (P < 0.01). The death rate in diarrheic control group was 100% by day 6. E. prostrata extracts (20 and 40 mg/kg), like norfloxacin, reduced the bacterial growth (P < 0.01), so that by the 6 ^th day Sd1 density was <100 and no death was recorded. There was a significant (P < 0.01) reduction in faeces frequencies. The extract exhibited notable (P < 0.01) inhibition of intestinal propulsion. Conclusion: The results suggest that E. prostrata possesses bactericidal and antidiarrheic properties and could be a therapeutic alternative for diarrheas of bacterial etiology.

Objective: To evaluate the antidiarrheal and antimicrobial activity of the extract of Stachytarpheta jamaicensis leaves. Materials and Methods: The methanolic extract of leaves of S. jamaicensis was prepared, with successive extraction in soxhlet apparatus with 300 ml of methanol for 24 h. The methanol extract of the leaves of S. jamaicensis (250 and 500 mg/kg) was studied for antidiarrheal activity using castor oil and magnesium sulphate-induced diarrhea models in mice. The antimicrobial activity of the extract (10 mg/ml) was determined by disk diffusion method. Results: At the doses of 250 and 500 mg/kg, the methanol extract showed significant antidiarrheal activity (P < 0.05). When tested for antibacterial activity, the methanol extract displayed moderate inhibitory activity against Escherichia coli, Staphylococcus epidermis and Pseudomonas aeruginosa, with an MIC value of 5.00 mg/ml. Conclusion: On the basis of these findings, it can be assumed that S. jamaicensis leaves could be a potential source for novel 'lead' discovery for antidiarrheal drug development.