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The developmental toxicity of orally administered theophylline in rats and mice
P Lindström1, R E Morrissey, J D George
1Systemic Toxicology Branch, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709.
Insights
Theophylline (THEO) developmental toxicity was assessed in rats and mice. Developmental effects occurred in rats at a dose without maternal toxicity, while mice showed effects linked to reduced water intake and weight gain.
Area of Science:
- Toxicology
- Developmental Biology
- Pharmacology
Background:
- Theophylline (THEO) is a common anti-asthmatic medication.
- Assessing developmental toxicity is crucial for medications used during pregnancy.
Purpose of the Study:
- To evaluate the developmental toxicity of theophylline in Sprague-Dawley rats and Swiss mice.
- To determine the no-observable-adverse-effect levels (NOAELs) for maternal and developmental toxicity.
Main Methods:
- Pregnant rats received theophylline in feed (0-0.40%) and mice in drinking water (0-0.20%) during critical gestation periods.
- Dose-intake estimations were calculated for both species.
- Maternal parameters (weight, consumption) and fetal outcomes (weight, malformations, resorptions) were assessed.
Main Results:
- Rats showed decreased fetal weight and litter size at 0.40% THEO, with no maternal toxicity at lower doses.
- Mice exhibited increased resorptions and decreased fetal weight at 0.15% and 0.20% THEO, coinciding with reduced maternal water consumption and weight gain.
- Maternal NOAELs were 218 mg/kg (rats) and 282 mg/kg (mice).
- Developmental NOAELs were 124 mg/kg (rats) and 282 mg/kg (mice).
Conclusions:
- Theophylline demonstrated developmental toxicity in rats at doses not causing overt maternal toxicity.
- In mice, developmental effects were associated with maternal toxicity and potential water deprivation.
- The determined NOAELs suggest a safety margin for human therapeutic use.
Abstract:
Theophylline (THEO), a widely prescribed anti-asthmatic, was evaluated for developmental toxicity. It was administered continuously on Gestational Days 6 through 15 to pregnant Sprague-Dawley (CD) rats in the feed (0, 0.15, 0.30, or 0.40%) and to pregnant Swiss (CD-1) mice in the drinking water (0, 0.075, 0.15, or 0.20%). Estimated intake of THEO for rats was 0, 124, 218, or 259 mg/kg/day, while for mice it was 0, 282, 372, or 396 mg/kg/day. In rats, maternal weight gain parameters (weight gain during gestation and treatment, as well as corrected weight gain) decreased at 0.40%. While food consumption was lower only in the 0.40% treatment group, water consumption was higher in all treated groups. There was a dose-related decreasing trend in gravid uterine weight. The number of live fetuses per litter decreased at 0.40% and the average male and female fetal weight per litter decreased at 0.30 and 0.40%. There was no increase in malformations. In mice, maternal corrected body weight and weight gain during gestation decreased at 0.15 and 0.20%, and weight gain during treatment and gravid uterine weight decreased at 0.20%. Water consumption was reduced by as much as 30-45% of controls at 0.15 and 0.20%, respectively, while food consumption did not change with THEO treatment. There was an increase in percentage resorptions per litter and a decrease in the average male and female fetal weight per litter at 0.15 and 0.20%. An increasing trend was noted for percentage malformed fetuses per litter, and percentage litters with externally malformed fetuses were slightly increased in the mid- and high-dose groups. However, these increases were not statistically significant. In summary, there were developmental effects seen in rats at a dose (0.30%) that did not produce overt maternal toxicity, but the adverse developmental effects in mice were observed at doses that caused reduced maternal water consumption and body weight gain. It is possible that water deprivation contributed to the effects seen in mice after THEO treatment. For maternal toxicity, no observable adverse effect levels (NOAELs) were 218 mg/kg for rats and 282 mg/kg for mice. NOAELs for developmental toxicity were 124 mg/kg for rats and 282 mg/kg for mice. These NOAELs are approximately 10- to 30-fold greater than doses required to maintain humans on serum THEO concentrations that are clinically useful.