Pharmacokinetics
Absorption
Bioavailability
30–55% of an oral dose absorbed from the GI tract in fasting adults; peak serum concentrations attained within 1–2 hours.
Following IM administration, peak serum concentrations generally attained more quickly and are higher than following equivalent oral doses.
Rapid IV administration results in peak serum concentrations immediately after completion of the infusion; serum concentrations may still be detectable 6 hours later.
Food
Food generally decreases rate and extent of absorption.
Distribution
Extent
Distributed into ascitic, synovial, and pleural fluids. Also distributed into liver, bile, lungs, gallbladder, prostate, muscle, middle ear effusions, bronchial secretions, sputum, maxillary sinus secretions, tonsils, saliva, sweat, and tears.
Distributed into CSF in concentrations 11–65% of simultaneous serum concentrations; highest CSF concentrations occur 3–7 hours after an IV dose.
Readily crosses the placenta. Distributed into milk in low concentrations.
Plasma Protein Binding
15–25%.
Protein binding is lower in neonates than in children or adults; ampicillin reportedly 8–12% bound to serum proteins in neonates.
Elimination
Metabolism
Partially metabolized by hydrolysis of the β-lactam ring to penicilloic acid which is microbiologically inactive.
Elimination Route
Eliminated in urine by renal tubular secretion and to a lesser extent by glomerular filtration. Small amounts also excreted in feces and bile.
In adults with normal renal function, approximately 20–64% of a single oral dose excreted unchanged in urine within 6–8 hours. Approximately 60–70% of a single IM dose or 73–90% of a single IV dose excreted unchanged in urine.
Half-life
0.7–1.5 hours in adults with normal renal function.
Half-life is 4 hours in neonates 2–7 days of age, 2.8 hours in neonates 8–14 days of age, and 1.7 hours in neonates 15–30 days of age.
Special Populations
Serum concentrations higher and more prolonged in premature or full-term neonates <6 days of age than in full-term neonates ≥6 days of age.
Renal clearance decreased in geriatric patients because of diminished tubular secretory ability; serum concentrations may be higher and half-life prolonged. In those 67–76 years of age, half-life ranges from 1.4–6.2 hours.
Serum concentrations are higher and half-life prolonged in patients with impaired renal function. Half-life may range from 7.4–21 hours in patients with Clcr <10 mL/minute
Stability
Storage
Oral
Capsules
Tight container at 15–30°C; avoid excessive heat.
For Suspension
Tight container at 15–30°C. After reconstitution, discard after 7 days if stored at room temperature or after 14 days if refrigerated.
Parenteral
Powder for Injection or Infusion
Solutions for IM injection or IV injection or infusion should be used within 1 hour after reconstitution and should not be frozen.
Compatibility
Parenteral
Solution Compatibility
| Compatible |
| Isolyte M or P with dextrose 5% |
| Incompatible |
| Amino acids 4.25%, dextrose 25% |
| Dextran 40 10% in sodium chloride 0.9% |
| Dextran 40 10% in dextrose 5% in water |
| Dextran 70 6% in sodium chloride 0.9% |
| Dextran 70 6% in dextrose 5% in water |
| Dextrose 5% in sodium chloride 0.9% |
| Dextrose 5 or 10% in water |
| Fat emulsion 10%, IV |
| Fructose 5.25% |
| Hetastarch 6% |
| Invert sugar 7.5% with electrolytes |
| Invert sugar 10% in water |
| Ringer’s injection, lactated |
| Sodium bicarbonate 1.4% |
| Sodium lactate (1/6) M |
| Variable |
| Ringer’s injection |
| Sodium chloride 0.9% |
Drug Compatibility
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