Toxicity of three drug solvents

The protective effects of 1,2-propanediol against radiation-induced hematopoietic injury in mice

Agents that provide protection against irradiation-induced hematopoietic injury are urgently needed for radiotherapy. We examined the effects of the small molecule, 1,2-propanediol (PPD), on total body irradiation (TBI)-induced hematopoietic injury in C57BL/6 mice. PPD administration 1 h before TBI significantly increased hematopoietic parameters such as white blood cell, platelet, red blood cell, and lymphocyte counts in vivo and enhanced the survival of mice exposed to TBI (7.0 and 7.5 Gy). PPD administration 1 h before TBI improved bone marrow (BM) and spleen recovery after TBI, with increases in both BM cellularity and spleen index. The number of colony-forming-units in bone marrow mononuclear cells (BMNCs) in vitro also increased significantly. PPD pretreatment increased the numbers of hematopoietic stem cells and hematopoietic progenitor cells in BM. Importantly, PPD also maintained endogenous antioxidant status by decreasing levels of malondialdehyde and increasing the expression of reduced glutathione, superoxide dismutase and catalase in the serum of irradiated mice. PPD alleviated the levels of apoptosis in HSCs induced by TBI, thus increasing the proportion of dividing BMNCs. These results suggest that PPD protects against TBI-induced hematopoietic injury through the increased activities of antioxidant enzymes and the inhibition of apoptosis in HSCs. PPD increased the serum levels of granulocyte-colony stimulating factor and interleukin-6 irrespective of TBI. In conclusion, these data suggest that PPD acts as a radioprotector against radiation-induced hematopoietic injury.

Interference of propylene glycol with the hole-board test

Experimental drugs and/or plant extracts are often dissolved in solvents, including propylene glycol. Nevertheless, there is evidence for psychoactive properties of this alcohol. In this study we found that in the hole-board test 10% propylene glycol did not modify the head-dipping behavior. However, 30% propylene glycol induced an increase in the number of head-dips (46.92 +/- 2.37 compared to 33.83 +/- 4.39, P<0.05, ANOVA/Student-Newman-Keuls), an effect comparable to that obtained with 0.5 mg/kg diazepam (from 33.83 +/- 4.39 to 54 +/- 3.8, P<0.01, ANOVA/Student-Newman-Keuls). These results demonstrate that 30% propylene glycol has significant anxiolytic effects in this model and therefore cannot be used as an innocuous solvent.

Relative efficacy of phenytoin and phenobarbital for the prevention of theophylline-induced seizures in mice

We evaluated the efficacy of pretreatment with phenytoin and phenobarbital to prevent seizures in mice given convulsive doses of theophylline. The control LD50 for theophylline was determined in 48 mice by intraperitoneal injections of increasing doses without anticonvulsant treatment. Anticonvulsant effects were determined in 105 additional mice pretreated with either phenytoin 30 mg/kg (n = 35), phenobarbital 35 mg/kg (n = 30), or phenobarbital 60 mg/kg (n = 40) one hour before theophylline administration. The theophylline LD50 (95% confidence interval) was 239 mg/kg (range, 229 to 248 mg/kg) for controls, 204 mg/kg (range, 194 to 214 mg/kg) for phenytoin, 305 mg/kg (range, 288 to 323 mg/kg) for low-dose phenobarbital, and 319 mg/kg (range, 307 to 331 mg/kg) for high-dose phenobarbital. Each LD50 differed significantly from control (P less than .05). The phenobarbital groups were significantly different from phenytoin (P less than .05) but not from each other. Theophylline serum concentrations were not significantly different among groups after adjustment for different doses. The mean +/- SEM time to seizure in minutes after adjustment for theophylline dose was 23.5 +/- 4.0 minutes for controls, 5.7 +/- 7.5 minutes for phenytoin, 44.1 +/- 7.1 minutes for low-dose phenobarbital, and 63.7 +/- 6.5 minutes for high-dose phenobarbital.(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacokinetic modeling of the anticonvulsant response of oxazepam in rats using the pentylenetetrazol threshold concentration as pharmacodynamic measure

This investigation developed strategies along which the anticonvulsant effect of oxazepam in the rat could be pharmacokinetically modeled. After determination of the pharmacokinetics of oxazepam, which could be described with a two-compartment model (half-lives of distribution and elimination 6 and 52 min, respectively), the drug was administered iv to groups of animals to achieve a serum concentration range of 0.1-2.5 mg/L at 10, 45, and 120 min after administration. At these time points pentylenetetrazol (PTZ) was infused slowly until the first myoclonic jerk occurred. The anticonvulsant response, expressed as the elevation of the serum or brain threshold concentration of PTZ, was modeled versus the serum (both total and free) and brain oxazepam concentration, according to the sigmoid Emax model. The total serum and brain oxazepam EC50 values are about 0.5 mg/L and 1.1 mg/kg, respectively, and Emax 120 mg/L PTZ. No marked differences in pharmacodynamic parameters between the three time groups were found, which indicates that serum and brain are pharmacokinetically indistinguishable from the effect compartment, that there is no (inter)activity of oxazepam metabolites and absence of development of acute tolerance during the investigated time frame. An interfering role of metabolites was also excluded by a direct radioreceptor assay of oxazepam, yielding very similar results as the specific chromatographic assay. It is concluded that the conception-anticonvulsant effect relationship of oxazepam can satisfactorily be described by the sigmoid Emax model, when utilizing the employed experimental strategies.

Biological effects of acetamide, formamide, and their monomethyl and dimethyl derivatives

The industrial use of certain acetamides and formamides (particularly DMAC and DMF) for their solvent properties has resulted in rather extensive examination of their biological properties. Both DMAC and DMF are rapidly absorbed through biological membranes and are metabolized by demethylation first to monomethyl derivatives and then to the parent acetamide or formamide. Relatively high single doses to various species following oral, dermal, i.p., i.v., or inhalation exposures generally are required to produce mortality. The liver is the primary target following acute high level exposure, but massive doses can also produce damage to other organs and tissues. Repeated sublethal treatment by various routes also shows the liver to be the target organ with the degree of damage being proportional to the amount absorbed. With MMF, the potential usefulness as a cancer chemotherapeutic agent needs to be measured against the hepatotoxic effects produced in man. Acetamides and formamides are generally inactive in mutagenicity tests. Mammalian test systems do not appear to be genetically sensitive and DMF has been recommended for use as the vehicle in microbial assays designed to test for genetic activity of hard-to-dissolve chemicals. Embryotoxicity can be demonstrated at high doses; doses which generally show toxicity to the maternal animals. Structural abnormalities in sensitive species such as the rabbit are produced following exposure at near-lethal levels. The spectrum of abnormalities seen is broad and fails to show any time or site specificity in terms of developing organs/organ systems. Inhalation exposures to DMAC and DMF at levels producing some maternal toxicity in rats have produced no teratogenic response and only slight evidence of embryotoxicity. Long-term feeding of relatively high levels of acetamide produces liver cancer in rats. DMAC and DMF appear to be noncarcinogenic. The environmental toxicity of these chemicals is low. Liver damage can be produced by overexposure to these chemicals in man. Airborne concentrations need to be controlled and care should be taken to avoid excessive liquid contact as the chemicals are absorbed through the skin. A relationship exists between the amount of DMAC or DMF absorbed and the amount of MMAC or MMF excreted in the urine so that biomonitoring of the urinary metabolites can indicate situations in which total exposures, both dermal and inhalation, are excessive. An interaction between DMF and ethanol occurs such that signs, including severe facial flushing, appear when DMF-exposed individuals consume alcoholic beverages.

Subchronic inhalation toxicity of dimethylformamide in rats and mice

Fisher F344 rats and B6C3F1 mice were exposed to concentrations of 0, 150, 300, 600 and 1200 ppm of dimethylformamide (DMF) for 6 hours a day, 5 days a week for 12 weeks. Detailed clinical observations were obtained weekly and body weights biweekly on all animals. Clinical chemistry and hematology evaluations were made on all rats and approximately half the mice at terminal sacrifice. Gross necropsy examinations were made on all animals. Histopathologic evaluations were conducted on selected tissues of animals of both species at all dose levels. Few overt signs of toxicity were seen in either rats or mice. There was a dose related depression in body weight gain in rats that was significant at the 1200 ppm level from the second week of study onwards. A total of 11 mice died or were sacrificed moribund during the study, 8 from the high dose and 2 from the 600 ppm dose level. Both clinical chemistry (in rats only) and gross necropsy observations, and histopathology of tissues indicate the possibility that liver may be the target in specific organ toxicity. The no-effect DMF dose was below the 150 ppm level for both rats and mice and the maximum tolerated dose was below the 600 ppm level.