Antimicrobial pharmacodynamics is the relationship between the concentration of an

antibiotic An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting bacterial infections, and antibiotic medications are widely used in the treatment and prevention ...

and its ability to inhibit vital processes of endo- or ectoparasites and

microbial A microorganism, or microbe,, ''mikros'', "small") and ''organism'' from the el, ὀργανισμός, ''organismós'', "organism"). It is usually written as a single word but is sometimes hyphenated (''micro-organism''), especially in olde ...

organisms.C.H. Nightingale, T. Murakawa, P.G. Ambrose (2002) Antimicrobial Pharmacodynamics in Theory and Clinical Practice Informa Health Care This branch of

pharmacodynamics Pharmacodynamics (PD) is the study of the biochemical and physiologic effects of drugs (especially pharmaceutical drugs). The effects can include those manifested within animals (including humans), microorganisms, or combinations of organisms ...

relates the concentration of an anti-infective agent to its effect, specifically to its antimicrobial effect.

Concentration-dependent effects

The

minimum inhibitory concentration In microbiology, the minimum inhibitory concentration (MIC) is the lowest concentration of a chemical, usually a drug, which prevents visible growth of a bacterium or bacteria. MIC depends on the microorganism, the affected human being (in vivo only ...

(MIC) and minimum bactericidal concentration are used to measure ''

in vitro ''In vitro'' (meaning in glass, or ''in the glass'') studies are performed with microorganisms, cells, or biological molecules outside their normal biological context. Colloquially called " test-tube experiments", these studies in biology a ...

'' activity of

antimicrobial An antimicrobial is an agent that kills microorganisms or stops their growth. Antimicrobial medicines can be grouped according to the microorganisms they act primarily against. For example, antibiotics are used against bacteria, and antifungals ar ...

agents. They are good indicators of antimicrobial potency, but don't give any information relating to time-dependent antimicrobial killing (the so-called post antibiotic effect).

Post-antibiotic effect

The post-antibiotic effect (PAE) is defined as persistent suppression of

bacterial Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were amon ...

growth after a brief exposure (1 or 2 hours) of bacteria to an

even in the absence of host defense mechanisms. Factors that affect the duration of the post-antibiotic effect include duration of antibiotic exposure, bacterial species, culture medium and class of antibiotic. It has been suggested that an alteration of DNA function is possibly responsible for the post-antibiotic effect following the observation that most inhibitors of protein and nucleic acid synthesis (

aminoglycosides Aminoglycoside is a medicinal and bacteriologic category of traditional Gram-negative antibacterial medications that inhibit protein synthesis and contain as a portion of the molecule an amino-modified glycoside ( sugar). The term can also re ...

, fluoroquinolones,

tetracyclines Tetracyclines are a group of broad-spectrum antibiotic compounds that have a common basic structure and are either isolated directly from several species of ''Streptomyces'' bacteria or produced semi-synthetically from those isolated compounds. T ...

clindamycin Clindamycin is an antibiotic medication used for the treatment of a number of bacterial infections, including osteomyelitis (bone) or joint infections, pelvic inflammatory disease, strep throat, pneumonia, acute otitis media (middle ear in ...

, certain newer macrolides/ ketolides, and

rifampicin Rifampicin, also known as rifampin, is an ansamycin antibiotic used to treat several types of bacterial infections, including tuberculosis (TB), ''Mycobacterium avium'' complex, leprosy, and Legionnaires’ disease. It is almost always used t ...

and

rifabutin Rifabutin (Rfb) is an antibiotic used to treat tuberculosis and prevent and treat ''Mycobacterium avium'' complex. It is typically only used in those who cannot tolerate rifampin such as people with HIV/AIDS on antiretrovirals. For active tuber ...

) induce long-term PAE against susceptible bacteria. Theoretically, the ability of an antibiotic to induce a PAE is an attractive property since antibiotic concentrations could fall below the MIC for the bacterium yet retain their effectiveness in their ability to suppress the growth. Therefore, an antibiotic with PAE would require less frequent administration and it could improve patient adherence with regard to pharmacotherapy. Proposed mechanisms include (1) slow recovery after reversible nonlethal damage to cell structures; (2) persistence of the drug at a binding site or within the periplasmic space; and (3) the need to synthesize new enzymes before growth can resume. Most antimicrobials possess significant in vitro PAEs (≥ 1.5 hours) against susceptible gram-positive cocci. Antimicrobials with significant PAEs against susceptible gram-negative bacilli are limited to carbapenems and agents that inhibit protein or DNA synthesis.Katzung basic and clinical pharmacology 13th edition 2015

References

{{Pharmacology Antibiotics Pharmacodynamics