Chapter 4: Special Populations (Children and Elderly)
The dosing of morphine in an infant to control pain typically requires using higher doses than an adult. The major reason for the higher dosing is
a. increased binding of drug to plasma proteins.
b. reduced entry of drug into the CNS.
c. reduced opiate sensitivity in young children.
d. reduced metabolism of drug.
e. increased clearance of drug.
Answer is d. Morphine is metabolized by glucuronosyl transferase to the 20-fold more active metabolite, 6-glucuronide morphine. The phase 2 glucuronidation pathway is significantly reduced in the neonate and as a result, drug glucuronidation is much less than in the adult. The glucuronidation pathway may take up to 3 to 4 years to fully develop. Thus, higher serum concentrations of morphine are required for infants to obtain effective analgesia.
The bioavailability of orally administered drugs is difficult to predict in infants because
a. the rate of transit of drugs through the infant GI tract is very rapid.
b. infants have very high first-pass metabolism.
c. absorption of drugs from the GI tract is reduced in neonates and changes with maturation.
d. the clearance of drugs by the kidney is very rapid in infants.
Answer is c. Absorption of drugs from the GI tract is reduced in neonates and changes with maturation making prediction of bioavailability of orally administered drugs very difficult (see Side Bar PEDIATRIC PHARMACOKINETICS—ABSORPTION). Some of the factors that alter absorption of drugs in the GI tract that change with age during the first several years of life include gastric pH, gastric emptying time, biliary function, metabolic enzymes in the GI tract, and development of intestinal flora.
Nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen should be avoided in the elderly because NSAIDs
a. have little efficacy in treating pain in older adults.
b. are more readily converted to toxic metabolites in older adults.
c. impair renal function in older adults.
d. impair hepatic function in older adults.
e. impair uptake of many nutrients from the GI tract in older adults.
Answer is c. Epidemiologic and clinical studies have demonstrated an association between ...