Pharmacokinetics of Amoxicillin
After learning about pharmacokinetics, Rita realizes the complexity of the interactions between the body and medications. Today, an athlete expressed concern to Rita about the frequency of one of his medications. He was recently prescribed the antibiotic amoxicillin for an upper respiratory tract infection. The antibiotic needs to be taken 3 times per day, and the athlete is having trouble remembering to take it. He asks Rita why the antibiotic has to be taken multiple times per day.
Question: Use a medication reference to review the pharmacokinetics of amoxicillin. Based on the pharmacokinetic and pharmacodynamic parameters, what factor would be most involved in the frequency of dosing?
Sample Answer
Pharmacokinetics of Amoxicillin
Considering the pharmacokinetics of amoxicillin, the first factor to consider is absorption. According to de Velde et al. (2016), amoxicillin is not affected by gastric acid and will be stable in the presence of such acid in the stomach. Amoxicillin is therefore absorbed quickly in the stomach after oral administration. According to Smith et al. (2018), orally administered doses of amoxicillin from 250 mg to 500 mg will cause average peak blood levels of the drug after one or two hours after the drug is administered.
Related to distribution which is a vital element of pharmacokinetics, amoxicillin will diffuse readily into body fluids and tissues with the exception of spinal and body fluid. According to Fournier et al. (2018), amoxicillin usually is 20% protein bound. Research has also indicated that the therapeutic levels of amoxicillin are present in interstitial fluids.
The final stage of the pharmacokinetics of amoxicillin is metabolism and excretion. According to De Velde et al. (2016), the half-life of amoxicillin is 61.3 minutes. According to Smith et al. (2018), nearly 60% of the dose of amoxicillin that will be orally administered will be excreted in urine within 6 to 8 hours. The amoxicillin that will be excreted in the urine will be unchanged.
The main factors that are considered in the frequency of dosage of amoxicillin among patients are the metabolism and excretion properties of the drug. Scholarly studies have therefore shown that the half-life of amoxicillin is 61.3. Experiments involving amoxicillin have also revealed that the drug is excreted in urine within 6 to 8 hours after oral administration (Fournier et al., 2018). A three-time per day dosage of amoxicillin is therefore essential. To ensure that the right concentrations of the drug are distributed across body tissues and fluids. A three-time dosage of amoxicillin, therefore, covers the six to eight hours intervals in which the drug is excreted (de Velde et al., 2016).
References
- De Velde, F., de Winter, B. C. M., Koch, B. C. P., van Gelder, T., & Mouton, J. W. (2016). Non-linear absorption pharmacokinetics of amoxicillin: consequences for dosing regimens and clinical breakpoints. Journal of Antimicrobial Chemotherapy, 71(10), 2909–2917. https://doi.org/10.1093/jac/dkw226
- Fournier, A., Goutelle, S., Que, Y. A., Eggimann, P., Pantet, O., Sadeghipour, F., Voirol, P., & Csajka, C. (2018). Population Pharmacokinetic Study of Amoxicillin-Treated Burn Patients Hospitalized at a Swiss Tertiary-Care Center. Antimicrobial Agents and Chemotherapy, 62(9). https://doi.org/10.1128/aac.00505-18
- Smith, P. W., Zuccotto, F., Bates, R. H., Martinez-Martinez, M. S., Read, K. D., Peet, C., & Epemolu, O. (2018). Pharmacokinetics of β-Lactam Antibiotics: Clues from the Past To Help Discover Long-Acting Oral Drugs in the Future. ACS Infectious Diseases, 4(10), 1439–1447. https://doi.org/10.1021/acsinfecdis.8b00160
