Bupropion Hydrochloride

Bupropion hydrochloride is a norepinephrine-dopamine disinhibitor (NDDI) approved for the treatment of depression and smoking cessation. Bupropion is a trimethylated monocyclic phenylaminoketone second-generation antidepressant, which differs structurally from most antidepressants, and resides in a novel mechanistic class that has no direct action on the serotonin system. Comprehensive chemical, physical, and spectroscopic profiles are presented. This analytical profile provides an extensive spectroscopic investigation utilizing mass spectrometry, one- and two-dimensional NMR, solid-state NMR, IR, NIR, Raman, UV, and X-ray diffraction. The profile also includes significant wet chemistry studies for pH, solubility, solution, and plasma stability. Both HPLC and UPLC methodology are presented for bupropion and its related impurities or major metabolites. The profile concludes with an overview of biological properties that includes toxicity, drug metabolism, and pharmacokinetics.

Influence of drug release properties of conventional solid dosage forms on the systemic exposure of highly soluble drugs

This study was designed to theoretically investigate the influence of drug release properties, characterized by the disintegration of a solid dosage form and dissolution of drug particles, on the systemic exposure of highly soluble drugs in immediate release products. An absorption model was developed by considering disintegration of a solid dosage form, dissolution of drug particles, gastrointestinal transit flow, and intestinal absorption processes. The absorption model was linked to a conventional pharmacokinetic model to evaluate the effect of disintegration and dissolution on the peak exposure (Cmax) and total exposure of area under the curve (AUC). Numerical methods were used to solve the model equations. The simulations show that the effect of disintegration of a dosage form and dissolution of drug particles depend on the permeability of a drug, with a low-permeability drug having a greater effect. To provide similar exposure to an oral solution formulation, a solid dosage form containing a low-permeability drug would need to dissolve more rapidly than a solid dosage form containing a high-permeability drug. It was shown theoretically for poorly permeable drugs that the disintegration rate constant has to be greater than 9 hour(-1)(equivalent to approximately 90% in 30 minutes) to make both AUC and Cmax ratios higher than.9, ensuring the confidence interval of.80 to 1.25. The rapid in vitro release requirement of at least 85% dissolved in 30 minutes is sufficient for highly soluble and highly permeable drugs. However, for highly soluble and poorly permeable drugs, the appropriate in vitro release requirement seems to be 90% dissolved in 30 minutes.

Decreased cisplatin/DNA adduct formation is associated with cisplatin resistance in human head and neck cancer cell lines

PURPOSE

To evaluate the correlation between cisplatin sensitivity, intracellular glutathione, and platinum/DNA adduct formation (measured by atomic absorption spectroscopy) in a series of seven head and neck cancer cell lines, and to evaluate the effect of biochemical modulation of glutathione on platinum/DNA adduct formation and repair.

METHODS

Cisplatin/DNA adducts were measured by atomic absorption spectroscopy. Glutathione content was measured by enzymatic assay and was modulated with buthionine sulfoximine. Apoptosis was measured by double-labeled flow cytometry.

RESULTS

Intracellular glutathione concentration was strongly correlated with cisplatin resistance (P = 0.002, R2 = 0.7). There was also a statistically significant inverse correlation between cisplatin/DNA adduct formation and the IC50 for cisplatin in these cell lines. (P = 0.0004, R2 = 0.67). In addition, resistant cells were able to repair approximately 70% of cisplatin/DNA adducts at 24 h, while sensitive cells repaired less than 28% of adducts in the same period. However, despite the positive correlation between cellular glutathione and cisplatin resistance, there was no direct correlation between intracellular glutathione concentration and platinum/DNA adduct formation. Further, depletion of intracellular glutathione by buthionine sulfoximine did not dramatically alter formation of cisplatin/DNA adducts even though it resulted in marked increase in cisplatin cytotoxicity and was associated with increased apoptosis.

CONCLUSIONS

These results suggest that glutathione has multiple effects not directly related to formation of cisplatin/DNA adducts, but may also be an important determinant of the cell's ability to repair cisplatin-induced DNA damage and resist apoptosis.

An evaluation of the hemizygous transgenic Tg.AC mouse for carcinogenicity testing of pharmaceuticals. I. Evidence for a confounding nonresponder phenotype

We have completed 2 26-wk studies to evaluate the hemizygous transgenic Tg.AC mouse, which has been proposed as an alternative short term model for testing carcinogenicity. We attempted to evaluate the response to the known rodent carcinogens cyclophosphamide, phenolphthalein, and tamoxifen and to the noncarcinogen chlorpheniramine following topical application. In the first study, a weak response (2/17 animals) was observed to the positive control 12-O-tetradecanoylphorbol 13-acetate (TPA in ethanol, 1.25 micrograms), and no response was observed to cyclophosphamide, phenolphthalein, or chlorpheniramine, despite evidence for skin penetration. The second study compared 1.25 micrograms and 6.25 micrograms of TPA in ethanol and acetone solutions. Tamoxifen was also evaluated in both solvents and orally. No significant response was observed to tamoxifen by skin paint or oral routes. Over 60% of the high dose TPA-treated animals showed no (0 or 1) papilloma response, and 30% of the animals each developed more than 32 papillomas. The heterogenous response to high dose TPA may be related to variability in the responsiveness of hemizygous animals. In light of these findings, further Tg.AC studies should employ homozygous animals, and the underlying cause for heterogeneity in the tumorigenic response of Tg.AC mice should be identified and eliminated.