Effect of Weight and/or Obesity on Ethambutol Drug Concentrations

Population Pharmacokinetics Analysis of Ethambutol in Overweight and Obese Volunteers

This study is designed to measure drug concentrations in the blood of healthy volunteers administered a single dose of ethambutol. Our hypothesis is that volunteers with a body mass index (BMI) 25-40 kg/m2 will remove ethambutol more quickly from the blood than leaner volunteers, and those with a BMI > 40 kg/m2 will have even greater clearance than those who are leaner.

Inclusion Criteria:

• Male and female volunteers, age 18 years of age or older, of all racial and ethnic origins. English and/or Spanish speaking volunteers are eligible to participate.
• We are recruiting 6 normal weight (BMI <25 kg/m2), 6 obese (BMI 25-40 kg/m2), and 6 extremely obese (BMI > 40 kg/m2) for this study. Half of each group will be male, the other half will be female.

Exclusion Criteria:

• Creatinine clearance < 70 ml/min as estimated by the Cockcroft-Gault equation.
• Pregnant or nursing or unwilling to use a reliable contraception method during the study period. The effects of ethambutol on pregnancy are unknown. In addition, the metabolic changes that accompany pregnancy may alter the concentration-time profile of ethambutol, so that the pregnancy and post-partum state would be a confounding variable.
• Abnormal liver function tests: transaminases >10 time the upper limit of normal, alkaline phosphatase > 5 time the upper limit of normal, total bilirubin >5 time the upper limit of normal.
• History of allergy to ethambutol.
• Ethambutol is contraindicated for any reason.
• Suspected or documented mycobacterial infection.
• History of gout.