An<unk>  is a chemical compound that inhibits or<unk> olishes the growth of microorganisms, such as bacteria, fungi, or protozoans. The term originally referred to any agent with biological activity against living organisms; however,<unk> " now is used to refer to substances with anti-bacterial, anti-fungal, or anti-parasitical activity. The first<unk>  compounds used in modern medicine were produced and isolated from living organisms, such as the penicillin class produced by fungi in the genus Penicillium, or streptomycin from bacteria of the genus Streptomyces. With advances in organic chemistry many<unk> s are now also obtained by chemical synthesis, such as the sulfa drugs. Many<unk> s are relatively small molecules with a molecular weight less than 2000 Da.
Unlike previous treatments for infections, which often consisted of administering chemical compounds such as strychnine and arsenic, with high toxicity also against mammals,<unk> s from microbes had no or few side effects and high effective target activity. Most anti-bacterial<unk> s do not have activity against viruses, fungi, or other microbes. Anti-bacterial<unk> s can be categorized based on their target specificity: "narrow-spectrum"<unk> s target particular types of bacteria, such as Gram-negative or Gram-positive bacteria, while broad-spectrum<unk> s affect a wide range of bacteria.
The effectiveness of individual<unk> s varies with the location of the infection, the<unk> ility of the<unk>  to reach the site of infection, and the<unk> ility of the microbe to inactivate or excrete the<unk> . Some anti-bacterial<unk> s destroy bacteria (bactericidal), whereas others prevent bacteria from multiplying (bacteriostatic).
Oral<unk> s are simply ingested, while intravenous<unk> s are used in more serious cases, such as deep-seated systemic infections.<unk> s may also sometimes be administered topically, as with eye drops or ointments.
In the last few years, three new classes of<unk> s have been brought into clinical use. This follows a 40-year hiatus in discovering new classes of<unk>  compounds. These new<unk> s are of the following three classes: cyclic lipopeptides (daptomycin), glycylcyclines (tigecycline), and oxazolidinones (linezolid). Tigecycline is a broad-spectrum<unk> , while the two others are used for gram-positive infections. These developments show promise as a means to counteract the growing bacterial resistance to existing<unk> s.
Antibiotic
Steroid
Antimicrobial
Analgesic
Antiviral drug
Sulfa drug
Anti inflammatory medications
Non-steroidal anti-inflammatory drug