This document discusses drug use in special situations including geriatric, pediatric, and pregnancy/lactation. For geriatric drug therapy, it notes that the elderly use more medications due to more disease symptoms and that aging affects drug pharmacokinetics through changes in absorption, distribution, metabolism and elimination. For pediatric drug therapy, it describes the developmental changes that influence drug response in infants and children. For drugs in pregnancy and lactation, it emphasizes avoiding non-essential drugs during pregnancy due to risks to the fetus, and that some drugs can pass through the placenta as a potential teratogen.

1. Drug use in special situations
• Geriatric drug therapy
• Pediatric drug therapy
• Drugs in Pregnancy &Lactation

2. GERIATRIC DRUG THERAPY
Geriatric (elderly) patients use more medications compared
to younger patients because they have more symptoms of
disease.
Clinical changes in elderly:
• Lean body mass diminishes by 20-30%.
• Fat free mass diminishes.
• Total albumin is reduced in elderly by 20%.
• There is 12% loss of tissue bone in male & 25% in female.
• The brain achieves its optimal potential at 16-20 years after
which there is slow decline in capabilities.
• Insulin clearance reduces.
• Blood concentrations, basal output & metabolic turnover of
major harmones like estrogen, testosterone, thyroxine,
androgen, angiotensin & aldosterone have reported to
decline with age.

3. Effect of aging on drugs
• Many of the Adverse Drug Reactions
encountered in elderly are the result of the
dose related pharmacokinetic changes.
• The aging process influences drug response by
interfering with fraction of drug absorbed (f),
plasma drug half life (t1/2), volume of
distribution (Vd) and drug clearance (CL) from
the body.

4. Factors governing drug use in special situations:
PHARMACOKINETICS
Age related changes influencing Absorption
• Reduced gastric acid secretion
• Impaired drug absorption
• GI motility & intestinal blood flow is reduced
• Collateral circulation bypassing liver
• Reduced active transport mechanism
Age related changes influencing Distribution
• Reduction in serum albumin concentration
• Reduction in erythrocyte binding
• Smaller volume of distribution due to reduced body water
• Increased volume of distribution for lipophilic drug due to
more fat

5. Age related changes influencing Metabolism
• Reduction in liver mass
• Reduced hepatic metabolizing enzymes
• Reduced liver blood flow
• Decrease in cytochrome P450
Age related changes influencing Elimination
• Reduction in total number of functioning nephrons
• Reduced renal plasma flow
• Reduced glomerular filtration rate
• Impaired renal tubular secretion

6. Age related PHARMACODYNAMIC changes in
elderly
• Depletion of neurotransmitters
• Decrease in baroreceptor activity
• Reduced responsiveness to beta adrenergic
receptors
• Increased pain tolerance
• Changes in laboratory values

7. PEDIATRIC DRUG THERAPY
• Drug treatment for infants & children requires
knowledge of drug response in early years of life.
Pharmacokinetic Factors:
• Pharmacokinetic changes occurs from few
months to 3 or 4 years of life.
Absorption
• Rate of absorption may be increased by the use
of liquid preparations.

8. Distribution
• Total volume of body water & extracellular fluid
related to body weight are greatest during
neonatal period & infancy.
• Blood brain barrier may be functionally
incomplete in neonates, which permits increased
penetration by some drugs
Metabolism
• Metabolism of most drugs proceeds comparatively
slowly in first few weeks of life & later increases up
to 2-3 years of life.
• After they reduce gradually until adolescence.

9. Elimination
• Drug metabolites are eliminated primarily through
bile or the kidneys. Renal elimination depends on:
A. Plasma protein binding
B. Renal blood flow
C. GFR
D. Tubular secretion
• All of these factors are altered in the first 2 yr of life.
Renal plasma flow is low at birth (12 mL/min) and
reaches adult levels of 140 mL/min by age 1 yr.
Similarly, GFR is 2 to 4 mL/min at birth, increases to
8 to 20 mL/min by 2 to 3 days, and reaches adult
levels of 120 mL/min.

10. Calculation of doses
• Individual dose = body weight(kg) × average adult dose
70
• Young’s Formula
• Child dose = age × adult dose
age + 12
• Diling’s Formula
• Child Dose = age × adult dose
20

11. DRUGS IN PREGNANCY & LACTATION
• The use of drugs during pregnancy must be
avoided unless absolutely necessary.
• The foetus or neonate must always be kept in
mind as a potential recipient of the drug.
• Placental barrier is selective membrane but
cannot block all the drugs from passing to
foetus.

12. FDA pregnancy category list

13. Teratogens
• A teratogen is an agent, which can cause a
birth defect.
• Teratogens are agents including viruses, drugs,
chemicals, stressors, and malnutrition, which
can impair prenatal development and lead to
birth defects or even death.
• Examples: Thalidomide, Phenytoin, Alchohol,
Viruses like Varicella, etc

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