Active Ingredient: Amoxicillin
Carbenicillin and ticarcillin are the two drugs in this class.
These agents are not effective against beta-lactamase producing organisms unless combined with a beta-lactamase inhibitor e. A ureido group plus a piperazine side chain produces piperacillin.A: According to Pharmacist's Letter, Amoxicillin our 8 year old temperature for at least 10 days.
The activity against Streptococci is slightly less that of the natural penicillins and ampicillin. As with the carboxypenicillins, drugs in this class are susceptible to inactivation by bacterial beta-lactamase production, unless combined with a beta-lactamase inhibitor e.
Pharmacodynamic Effects When choosing an antimicrobial agent and designing appropriate dosing regimens for the drug, it is important to consider spectrum of activity, but also incorporate known pharmacodynamic principles about the drug.
In this manner, efficacy can potentially be maximized while toxicity can be minimized.
However, once the drug concentration falls below the level of the MIC and the PAE has ceased, the kill rate diminishes. Generally, the more dense the bacterial population i.
The bactericidal activity of the penicillins does not appear to be affected by changes in pH or oxygen tension. Penicillins and other beta-lactams do not penetrate well into phagocytes 104, thus limiting their ability to kill intracellular pathogens.
In addition, penicillins only exert their bactericidal effect on bacteria that are actively replicating. Synergistic Bactericidal Activity Combinations of a beta-lactam plus another agent, such as an aminoglycoside, kill some organisms most effectively.
In these cases, antibacterial synergy occurs. Synergy is defined as an effect, such as bactericidal activity, that is significantly greater with the combination than the sum of the two agents when used alone.
Enterococcal endocarditis is such an example, as penicillin monotherapy results in bacteriostatic activity and very high relapse rates after treatment 149, while the combination of penicillin plus an aminoglycoside is bactericidal 157.
Antagonism of Antibacterial Combinations Antibacterial antagonism is defined as a resulting effect that is significantly less in combination than with either of the two drugs when used as monotherapy.
This effect has been demonstrated with the penicillins in combination with chlortetracycline in patients with pneumococcal meningitis, when penicillin monotherapy was more effective that the combination of agents 133.
Also, the use of chloramphenicol has decreased dramatically in the last decade due to the availability of newer agents that are equally efficacious and less toxic.
Antagonism can also occur due to a physical incompatibility with inactivation between two drugs when infused together. This can occur with carbenicillin or ticarcillin with an aminoglycoside.
These drugs should therefore not be mixed in the same infusion. Post-Antibiotic Effect The PAE is defined as a persistent suppression of bacterial growth after effective exposure to an antimicrobial agent when serum concentrations of the drug have fallen to levels below the MIC.
This effect differs between infecting organisms and between drugs. The length of the PAE can range from 0-6 hours Table 4, depending upon the penicillin. As stated previously, the type of organism can affect the PAE.
The penicillins do not exhibit an appreciable PAE against gram-negative organisms.
Also, combinations of antimicrobial agents can result in a synergistic PAE. This implies that increased duration of drug exposure above the MIC would be more predictive of positive outcome versus increased drug doses and subsequent increased peak concentrations.
One study examined combinations of carbenicillin plus continuous infusion cefamandole, carbenicillin plus intermittent cefamandole, and carbenicillin plus continuous infusion tobramycin in febrile, neutropenic cancer patients 32.