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Thermodynamic study of the transfer of acetanilide and phenacetin from water to different organic solvents.

The molar (K(C)(o/w)) and rational (K(X)(o/w)) partition coefficients in the octanol/buffer, i-propyl myristate/buffer, chloroform/buffer, and cyclohexane/buffer systems were determined for acetanilide and phenacetin at 25.0, 30.0, 35.0, and 40.0 degrees C. In all cases except for cyclohexane, the K(C)(o/w) and K(X)(o/w) values were greater than unity. This demonstrates that these two drugs have predominantly lipophilic behavior. Gibbs and van't Hoff thermodynamic analyses have revealed that the transfer of these drugs from water to organic solvents is spontaneous and that it is mainly driven enthalpically for i-propyl myristate and chloroform, and entropy-driven for octanol and cyclohexane.

Acetanilides↗

Metabolite kinetics: formation of acetaminophen from deuterated and nondeuterated phenacetin and acetanilide on acetaminophen sulfation kinetics in the perfused rat liver preparation.

The role of hepatic intrinsic clearance for metabolite formation from various precursors on subsequent metabolite elimination was was investigated in the once-through perfused rat liver preparation. Two pairs of acetaminophen precursors: [14C] phenacetin-d5 and [3H] phenacetin-do, [14C] acetanilide and [3H] phenacetin were delivered by constant flow (10 ml/min/liver) either by normal or retrograde perfusion to the rat liver preparations. The extents of acetaminophen sulfation were compared within the same preparation. The data showed that the higher the hepatocellular activity (intrinsic clearance) for acetaminophen formation, the greater the extent of subsequent acetaminophen sulfation. The findings were explained on the basis of blood transit time and metabolite "duration time." Because of blood having only a finite transit time in liver, the longer the drug requires for metabolite formation, the less time will remain for metabolite sulfation and the less will be the degree of subsequent sulfation. Conversely, when the drug forms the primary metabolite rapidly, a longer time will remain for the metabolite to be sulfated in liver to result in a greater degree of metabolite sulfation. Finally, the effects of hepatic intrinsic clearances for metabolite formation and zonal distribution of enzyme systems for metabolite formation and elimination in liver are discussed.

Acetaminophen↗

The pharmacology and toxicology of meta-substituted acetanilide I: acute toxicity of 3-hydroxyacetanilide in mice.

Toxicity of meta or 3-hydroxyacetanilide was evaluated in mice. The LD50 was 1025 mg/kg when given intraperitoneally (i.p.). The drug in doses greater than 400 mg/kg i.p. caused significant sedation. 3-Hydroxyacetanilide, 900 mg/kg i.p., did not cause hepatic necrosis evaluated by either histology or changes in plasma glutamate pyruvate transaminase activity. Acetaminophen (4-hydroxyacetanilide, paracetamol) caused significant liver glutathione depletion two hours after dosing. In contrast, liver glutathione was only slightly decreased by 600 mg/kg i.p. of 3-hydroxyacetanilide at 2 or 4 hours after the dose. It is suggested that the meta-substituted acetanilide derivatives might be safer analgesics and antipyretics than acetaminophen.

Acetaminophen↗

Gas-liquid chromatographic determination of alachlor (2-chloro-2', 6'-diethyl-N-(methoxymethyl)-acetanilide) herbicide residues in corn and soybeans.

A method has been developed for the extraction and determination of alachlor (2-chloro-2',6'-diethyl-N- (methoxymethyl)-acetanilide) residues in green corn and soybeans. Residues are extracted with acetonitrile and cleaned up on a Florisil column. The methylene chloride extract is sufficiently clean for electron capture gas-liquid chromatographic analysis and for verification by thin layer chromatography. Average recoveries of spiked samples (0.2 ppm) were 69 and 82% for corn and soybeans, respectively. This procedure could be useful for the detection of the parent compound in these crops soon after field application, but it does not detect metabolites.

Acetanilides↗

Evidence of chemical stimulation of hepatic metabolism by an experimental acetanilide (FOE 5043) indirectly mediating reductions in circulating thyroid hormone levels in the male rat.

N-(4-Fluorophenyl)-N-(1-methylethyl)-2-[[5-(trifluoromethyl)-1,3, 4-thiadiazol-2-yl]oxy]acetamide (FOE 5043) is a new acetanilide-type herbicide undergoing regulatory testing. Previous work in this laboratory suggested that FOE 5043-induced reductions in serum thyroxine (T4) levels were mediated via an extrathyroidal site of action. The possibility that the alterations in circulating T4 levels were due to chemical induction of hepatic thyroid hormone metabolism was investigated. Treatment with FOE 5043 at a rate of 1000 ppm as a dietary admixture was found to significantly increase the clearance of [125I]T4 from the serum, suggesting an enhanced excretion of the hormone. In the liver, the activity of hepatic uridine glucuronosyl transferase, a major pathway of thyroid hormone biotransformation in the rat, increased in a statistically significant and dose-dependent manner; conversely, hepatic 5'-monodeiodinase activity trended downward with dose. Bile flow as well as the hepatic uptake and biliary excretion of [125I]T4 were increased following exposure to FOE 5043. Thyroidal function, as measured by the discharge of iodide ion in response to perchlorate, and pituitary function, as measured by the capacity of the pituitary to secrete thyrotropin in response to an exogenous challenge by hypothalamic thyrotropin releasing hormone, were both unchanged from the controlled response. These data suggest that the functional status of the thyroid and pituitary glands has not been altered by treatment with FOE 5043 and that reductions in circulating levels of T4 are being mediated indirectly through an increase in the biotransformation and excretion of thyroid hormone in the liver.

Acetamides↗

The degradation of paracetamol (4-hydroxyacetanilide) and other substituted acetanilides by a Penicillium species.

A mould which was isolated from a solution of paracetamol was identified as a Penicillium species and was found to possess the ability to utilise a series of substituted acetanilides, including paracetamol (4-hydroxyacetanilide), phenacetin (4-ethoxyacetanilide) and metacetamol (3-hydroxyacetanilide) as sole carbon sources for growth. Studies with washed-cell suspensions indicated that growth of the Penicillium isolate in the presence of paracetamol induced the respective enzyme systems for the degradation of this compound. Manometric studies measuring oxygen uptake rates, indicated that the mould was capable of degrading paracetamol to acetate and 4-aminophenol. Acetate was further metabolised whilst 4-aminophenol accumulated in the growth medium and was subsequently i-entified by UV spectroscopy and thin-layer chromatography. Similar experiments with phenacetin indicated metabolism by the mould to acetate and 4-ethoxyaniline which was isolated and identified by subsequent analysis of the growth medium. However, unlike 4-aminophenol and 4-ethoxyaniline, the degradation product (3-aminophenol) from metacetamol metabolism was further degraded by the mould.

Acetaminophen↗

Energy of charged states in the acetanilide crystal: trapping of charge-transfer states at vacancies as a possible mechanism for optical damage.

Calculations for the acetanilide crystal yield the effective polarizability (16.6 A(3)), local electric field tensor, effective dipole moment (5.41 D), and dipole-dipole energy (-12.8 kJ/mol). Fourier-transform techniques are used to calculate the polarization energy P for a single charge in the perfect crystal (-1.16 eV); the charge-dipole energy W(D) is zero if the crystal carries no bulk dipole moment. Polarization energies for charge-transfer (CT) pairs combine with the Coulomb energy E(C) to give the screened Coulomb energy E(scr); screening is nearly isotropic, with E(scr) approximately E(C)/2.7. For CT pairs W(D) reduces to a term deltaW(D) arising from the interaction of the charge on each ion with the change in dipole moment on the other ion relative to the neutral molecule. The dipole moments calculated by density-functional theory methods with the B3LYP functional at the 6-311++G(**) level are 3.62 D for the neutral molecule, changing to 7.13 D and 4.38 D for the anion and cation, relative to the center of mass. Because of the large change in the anion, deltaW(D) reaches -0.9 eV and modifies the sequence of CT energies markedly from that of E(scr), giving the lowest two CT pairs at -1.98 eV and -1.41 eV. The changes in P and W(D) near a vacancy are calculated; W(D) changes for the individual charges because the vacancy removes a dipole moment and modifies the crystal dielectric response, but deltaW(D) and E(C) do not change. A vacancy yields a positive change DeltaP that scatters a charge or CT pair, but the change DeltaW(D) can be negative and large enough to outweigh DeltaP, yielding traps with depths that can exceed 150 meV for single charges and for CT pairs. Divacancies yield traps with depths nearly equal to the sum of those produced by the separate vacancies and so they can exceed 300 meV. These results are consistent with a mechanism of optical damage in which vacancies trap optically generated CT pairs that recombine and release energy; this can disrupt the lattice around the vacancy, thereby favoring trapping and recombination of CT pairs generated by subsequent photon absorption, leading to further lattice disruption. Revisions to previous calculations on trapping of CT pairs in anthracene are reported.

Journal Article↗