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Effect of infant age on aminopyrine breath test results
Insights
Infant liver enzyme activity matures with age, as shown by the aminopyrine breath test. Hepatic N-demethylase function in infants approaches adult levels by 20 weeks, indicating developmental changes in drug metabolism.
Area of Science:
- Pharmacology
- Pediatrics
- Biochemistry
Background:
- The aminopyrine breath test is a validated method for assessing hepatic N-demethylase activity in adults.
- Understanding the maturation of liver enzyme function in infants is crucial for pediatric pharmacology and drug safety.
Purpose of the Study:
- To investigate the developmental changes in hepatic N-demethylase activity in infants using the 13C aminopyrine breath test.
- To establish the age at which infant liver enzyme function reaches adult levels.
Main Methods:
- Oral administration of 13C aminopyrine (2 mg/kg) to 16 infants aged 1-38 weeks.
- Collection of breath samples for 6 hours post-administration to measure 13CO2 enrichment.
- Exclusion of absorption as a variable by comparing oral and intravenous administration routes.
Main Results:
- Aminopyrine demethylation, measured by 13CO2 elimination, showed a positive correlation with infant age.
- Infant metabolic rates approached adult levels by approximately 20 weeks of age.
- Nutritional status and feeding route did not alter the observed maturational effects on aminopyrine elimination.
Conclusions:
- Significant maturational differences exist in infant aminopyrine metabolism.
- These differences likely stem from immature N-demethylase activity or alternative metabolic pathways for formaldehyde in infants.
Unlabelled:
The aminopyrine breath test has been used in adults as a measure of hepatic N-demethylase activity. In order to study maturational changes in enzyme function, 13C aminopyrine (2 mg/kg) was administered orally to infants (n = 16) between the ages of 1 and 38 wk. Breath samples were collected for 6 h after administration of the labeled aminopyrine for the measurement of 13CO2 enrichment. Using a number of different scoring methods to quantitate 13CO2 elimination of breath, demethylation of aminopyrine was found to be positively correlated to age. By 20 wk of age, some infants had rates of elimination similar to those measured in adults. Absorption was excluded as a limiting variable, because no improvement in oxidation rates was found when the aminopyrine was readministered as an intravenous bolus. Changes in nutritional status and route of feeding (enteral versus parenteral) did not prevent the effect of maturation on aminopyrine elimination.
Conclusions:
1) maturational differences are seen in the metabolism of aminopyrine; 2) these differences may reflect immaturity of N-demethylase activity or diversion of the liberated formaldehyde into biosynthetic rather than oxidative pathways.