Peak Prostate Concentration of Oral Amoxicillin
Direct Answer
The available evidence does not provide specific data on peak prostate concentration achieved with 1 gram of oral amoxicillin. The pharmacokinetic studies examining antibiotic penetration into prostatic tissue have not included amoxicillin in their investigations.
Available Pharmacokinetic Data
Serum Concentrations
- After 1 gram of oral amoxicillin, the mean peak serum level is approximately 9.90 mg/L (μg/mL), achieved within 1-2 hours of administration 1
- Approximately 70% of the drug is excreted in urine during the first 6 hours 1
Prostate Penetration Data Gap
- No published studies have directly measured amoxicillin concentrations in prostatic tissue or prostatic fluid following oral administration 2, 3, 4
- The available research on prostatic antibiotic penetration has focused on other agents including fluoroquinolones (ofloxacin, moxifloxacin), aminoglycosides (amikacin), tetracyclines (minocycline), and other beta-lactams (piperacillin, ampicillin-sulbactam) 2, 3, 4, 5
Extrapolation from Related Beta-Lactam Data
Ampicillin-Sulbactam as a Proxy
- Ampicillin-sulbactam, a closely related aminopenicillin, demonstrates a prostate tissue/plasma ratio of approximately 0.37 5
- If amoxicillin behaves similarly to ampicillin in prostatic penetration, the estimated peak prostate concentration after 1 gram oral amoxicillin would be approximately 3.7 mg/L (0.37 × 9.90 mg/L serum concentration)
- However, this is speculative and not based on direct measurement 5
Piperacillin Comparison
- Piperacillin, another beta-lactam, shows a prostatic tissue/serum ratio of only 0.21 ± 0.15, which was significantly lower than fluoroquinolones 2
- This suggests beta-lactams generally have poor prostatic penetration compared to other antibiotic classes 2
Clinical Context
Amoxicillin for Prostatitis
- Amoxicillin is not recommended as a first-line agent for bacterial prostatitis due to lack of efficacy and pharmacokinetic data in this indication 6
- Fluoroquinolones (ciprofloxacin, levofloxacin, moxifloxacin) achieve prostatic tissue/serum ratios of 1.0-1.6, making them superior choices for prostatic infections 3, 4
- Moxifloxacin achieves prostatic fluid concentrations of 3.8 ± 1.2 mg/L after a single 400 mg oral dose, with a prostatic fluid/plasma ratio of 1.6 4
Amoxicillin Use in Other Contexts
- Amoxicillin has been studied for anthrax prophylaxis at 500 mg every 8 hours for adults, but not specifically for prostatic tissue penetration 6
- High-dose amoxicillin (4 g/day for adults) is recommended for respiratory infections, but prostatic concentrations at these doses remain unmeasured 6, 7, 8
Key Limitations
- The absence of prostatic pharmacokinetic studies for amoxicillin represents a significant knowledge gap in the literature
- Extrapolation from other beta-lactams suggests poor prostatic penetration, but direct measurement is needed for definitive conclusions 2, 5
- The clinical relevance of prostatic tissue concentrations depends on the minimum inhibitory concentration (MIC) of the target pathogen, which varies by organism 6