Dissolution profiles of four carbamazepine immediate-release generic products (200 mg tablets) and the reference product Tegretol® were evaluated using the USP paddles method and an alternative method with the flow-through cell system, USP Apparatus 4. Under official conditions all products met the Q specification, dissolution profiles of generic products were similar to the dissolution profile of the reference product (f 2 > 50) and model-independent parameters showed non significant differences to the reference product except mean dissolution time for product A (p < 0.05). On the other hand, when the flow-through cell system was used, none of the products met the pharmacopeial specification at 15 min and product A did not reach dissolution criteria at 60 min, dissolution profiles of all generic products were not similar to the reference product profile (f 2 < 50) and all model-independent parameters showed significant differences compared to the reference product (p < 0.05). Weibull's model was more useful for adjusting the dissolution data of all products in both USP apparatuses and Td values showed significant differences compared to the reference product (p < 0.05) when USP Apparatus 4 was used. These results indicate that the proposed method, using the flow-through cell system, is more discriminative in evaluating both, rate and extent of carbamazepine dissolution process from immediate-release generic products.

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The antispasmodic activity of extracts from the aerial parts of Buddleja scordioides and Buddleja perfoliata (family: Scrophulariaceae) was studied on isolated tissue preparations from rabbit and guinea pig intestine. The chloroformic extract from the plants exhibited a significant relaxation on the spontaneous contraction of isolated rabbit jejunum at concentrations ranging from 1 to 400 m mg/ml, and also caused an inhibitory effect on both K ؉ and Ca 2؉ induced contractions in the same tissue. The extracts at moderate doses (50 m mg/ml) reduced 5-hydroxytryptamine (5-HT), acetylcholine and histamine induced contractions on isolated guinea pig ileum. Therefore, B. scordioides and B. perfoliata possess similar relaxant mechanism of action, in view of the fact that both inhibit K ؉ induce contraction and act through serotoninic, muscarinic and histaminic receptors. So, these data support the idea that the extracts may interfere either with calcium mobilization from intracellular stores, or with calcium interaction with regulatory proteins (e.g., calmodulin), or in other steps in the calcium signaling pathway. This leads us to suggest that the spasmolytic effect of both Buddleja species on smooth muscular contractility are due to the same or similar compounds occurring in these two species, which might be present in similar quantities.

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Preclinical Research The current work evaluates the interaction between two commonly used drugs, tramadol (Tra) and gabapentin (Gbp). Dose-response curves (DRC) and isobolographic analysis were used to confirm their synergistic antihyperalgesic and anti-allodynic responses in a rat neuropathic pain model involving chronic constriction injury of the sciatic nerve and in von Frey and acetone tests. Tra and Gbp produced dose-dependent antihyperalgesic and anti-allodynic effects. Dose-response studies of combinations of Tra and Gbp in combination showed the DRC was leftward-shifted compared to the DRCs for each compound alone. One combination demonstrated both antihyperalgesic and anti-allodynic effects greater than those observed after individual administration. The remaining combinations demonstrated an additive effect. The Tra+Gbp combination demonstrated a potentiative effect with smaller doses of Tra. Additionally, it was determined lethal dose 50 (LD50 ) of Tra alone and tramadol + Gbp 10 using mice to 48 h post administration. The DRC (death) were similar for Tra alone and in Tra in combination, despite the improved effectiveness of Tra in the presence of GBP, 10 mg/kg. A combination of these drugs could be effective in neuropathic pain therapy because they can produce potentiative (at a low dose) or additive effects. Drug Dev Res 77 : 217-226, 2016.   © 2016 Wiley Periodicals, Inc.

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