1. We report two members of a new class of potent positive inotropic agents, 4,5-dihydro-6-[4-(1H-imidazol-1-yl)phenyl]-3(2H)-pyridazinones (1 and 2). Compound 2 is the most potent nonsympathomimetic, noncardiac glycoside cardiotonic agent reported to date. A linear regression analysis of log(AD-ED₅₀) versus log(PDE) inhibition yielded the equation log AD-ED₅₀ = 0.56 log(PDE) - 1.60 (r = 0.89, s = 0.32, n = 6), strongly indicating the primary mechanism of positive inotropic action is inhibition of fraction III cardiac phosphodiesterase. Molecular modeling of diverse cardiotonics (1, 2, amrinone, milrinone, fenoximone) revealed spatial/electronic similarities, leading to a five-point model for activity: (1) strong carbonyl dipole, (2) adjacent acidic proton, (3) methyl-sized lipophilic space, (4) flat topography, (5) basic/hydrogen bond acceptor opposite the dipole. 2. (-)-Sparteine (1), an antiarrhythmic alkaloid, is oxidized by cytochrome P-450 to Δ²- and Δ⁵-dehydrosparteine. We investigated N-oxide intermediacy: rat liver microsomes metabolized 1/α-isosparteine (7) to iminium derivatives 3/9, but synthetic N-oxides (8,13) did not form these products. N-oxides were stable, did not accumulate, and kinetic isotope effects (2.8 for 1, 2.3 for 7) matched N-dealkylation via aminium ions (not N-oxide decomposition). Proposed mechanism: oxygenated P-450 abstracts nitrogen electron to form aminium radical, which loses α-hydrogen to form carbon radical; oxygen rebound forms carbinolamine, which dehydrates to iminium product. Thus, N-oxides are not intermediates in P-450-mediated sparteine dealkylation. 3. A series of novel 3-quinolinecarboxylic acid derivatives were prepared and evaluated for antibacterial activity, characterized by 6-position fluorine and 1-/7-position substituted amino groups. Structure-activity relationships showed maximal potency when 1-substituent was methylamino and 7-substituent was 4-methyl-1-piperazinyl (16) or 1-piperazinyl (21). Derivatives 16 (amifloxacin, 1-methylamino pefloxacin analogue) and 21 (1-methylamino norfloxacin analogue) had potency comparable to reference agents. For 16 against Escherichia coli Vogel: in vitro MIC = 0.25 μg/mL; in vivo (mice) PD₅₀-₉₀ = 1.0 mg/kg (PO), 0.6 mg/kg (sc).