Category:Anti-infectives

An anti-infective is a medicine used to treat or prevent infection by a microorganism pathogenic to humans. The category is the broadest in clinical pharmacology and includes the antibacterials, the antifungals, the antivirals, the antiparasitics (including the antiprotozoals and the anthelmintics), the antimycobacterials (tuberculosis and atypical-mycobacterial medicines), and the antiseptics and disinfectants used on surfaces rather than systemically. The unifying feature of the category is the strategy of selective toxicity: each anti-infective must exploit a molecular or biochemical feature of the microorganism that the human host either lacks or differs from, so that the medicine can kill or inhibit the pathogen at concentrations the host can tolerate. The narrower the difference between pathogen and host, the harder the selective-toxicity problem; this is why the antibacterials (whose targets are mostly absent from human cells) are the largest and best-established sub-category, while the antifungals and antivirals (whose targets are more often shared with the host) are smaller and have more difficult therapeutic-index management.

The antimicrobial era opened, in clinical terms, in 1909 with Paul Ehrlich and Sahachiro Hata's arsphenamine (Salvarsan) for syphilis, the first medicine to cure a specific bacterial infection by a selective chemical principle. The sulfonamide era began with Domagk's Prontosil in 1935, and the natural-product antibiotic era with Fleming's 1928 observation of penicillin (clinical use waited until Florey and Chain purified the active principle at Oxford from 1940). The antifungal era began with the Hazen-and-Brown 1950 isolation of nystatin at the New York State Department of Health; the antiviral era with the Yale chemist Prusoff's idoxuridine in 1962 and definitively with Elion's acyclovir in 1977. The histories of each sub-category are described in detail on the respective umbrella pages.

The clinical use of an anti-infective rests on the same three judgments described under antibacterials and extended to the broader pathogen list: which organism is likely to be causing the infection; which medicines retain activity against it in this population at this time; and what dose, route, and duration deliver enough medicine to the site of infection. Each of those judgments is made under uncertainty: empirical treatment is often required before microbiological identification; local resistance patterns shift on a timescale of months in hospital settings and years in community ones; and the pharmacokinetics of medicine penetration to specific tissues (the cerebrospinal fluid, the prostate, the lung in cystic fibrosis, the bone) differs substantially across the anti-infective classes.

The contemporary anti-infective field is dominated by three overlapping concerns. The first is antimicrobial resistance, originally recognised in penicillin-resistant Staphylococcus aureus in 1944 and now extending across most antibacterial classes (MRSA, VRE, ESBL-producing Enterobacterales, CRE including KPC and NDM and OXA carbapenemases, multidrug-resistant Pseudomonas and Acinetobacter), into the azole-resistant Aspergillus species, into Candida auris as a multi-class resistant emerging pathogen, into the parasites that cause malaria (chloroquine, then sulfadoxine-pyrimethamine, then artemisinin partial resistance), and into HIV in the absence of fully suppressive antiretroviral therapy. The second is the pipeline problem: the rate of approval of new antibacterials in particular has not kept pace with the rate of resistance emergence, and several of the major pharmaceutical companies have withdrawn from antibacterial discovery on commercial grounds. The third is the stewardship problem: anti-infectives, particularly antibacterials, are prescribed unnecessarily often (for self-limited viral upper respiratory illness, for asymptomatic bacteriuria, for surgical prophylaxis extending beyond evidence-based duration), and the unnecessary use accelerates resistance without therapeutic benefit. Antimicrobial stewardship programmes have become a routine part of hospital practice over the past fifteen years.

The vaccinology counterpart of the category, although a separate pharmacological field, has had cumulative clinical consequences as large as the anti-infectives themselves. The eradication of smallpox in 1980 by global vaccination, the near-elimination of poliomyelitis in most of the world, the substantial reduction of diphtheria, tetanus, pertussis, measles, mumps, rubella, Haemophilus influenzae type b, pneumococcal disease, and rotavirus by routine immunisation, the human papillomavirus vaccine programmes now reducing cervical and oropharyngeal cancer incidence, and the SARS-CoV-2 mRNA and adenovirus-vectored vaccines that within twelve months of the pandemic onset reduced COVID-19 mortality substantially in vaccinated populations, are achievements at the same scale as the discovery of the antibacterials. The vaccines are listed under biologics rather than here, but the conceptual relationship to the anti-infective category is close.

• Antibacterials: the largest sub-category by both number and clinical use; includes the natural-product antibiotics (penicillins, cephalosporins, carbapenems, aminoglycosides, tetracyclines, macrolides, glycopeptides, lipopeptides) and the synthetic classes (sulfonamides, fluoroquinolones, nitroimidazoles, nitrofurans, oxazolidinones)
• Antifungals: polyenes, azoles (imidazoles and triazoles), echinocandins, allylamines, flucytosine, griseofulvin, hydroxypyridones
• Antivirals: the herpesvirus medicines, the influenza medicines and neuraminidase inhibitors, the antiretrovirals for HIV (the nucleoside, non-nucleoside, protease, integrase, and entry inhibitors), the hepatitis B and C antivirals (including the curative direct-acting antiviral combinations for hepatitis C), the SARS-CoV-2 antivirals
• Antiparasitics including:
  • Antiprotozoals: medicines for malaria (antimalarials including chloroquine, hydroxychloroquine, mefloquine, atovaquone-proguanil, primaquine, and the artemisinin-based combination therapies), for amoebiasis, giardiasis, trichomoniasis, leishmaniasis, trypanosomiasis, toxoplasmosis
  • Anthelmintic medicines: albendazole, mebendazole, praziquantel, ivermectin, pyrantel pamoate
  • Ectoparasitic medicines: permethrin, ivermectin, spinosad, malathion
• Antimycobacterial agents (collected separately when the category is built): isoniazid, rifampin, pyrazinamide, ethambutol, the second-line and multidrug-resistant-tuberculosis medicines (bedaquiline, delamanid, pretomanid, the older injectable agents amikacin and kanamycin and capreomycin, the fluoroquinolones in their tuberculosis indication, linezolid for XDR-TB), the leprosy regimens (dapsone, rifampin, clofazimine)
• Antiseptics and disinfectants (surface or topical, not systemic): chlorhexidine, povidone-iodine, hypochlorite, alcohols, hydrogen peroxide, the silver-based preparations

The boundary of this category is "medicine prescribed to kill, inhibit, or prevent infection by a microorganism." The vaccines that prevent infection through induced immune response, although they share the clinical goal, are not anti-infectives in the strict pharmacological sense and are listed under biologics. Medicines that treat the consequences of infection rather than the infection itself (intravenous fluids for sepsis, vasopressors for septic shock, the supportive-care medicines for severe infections) are not anti-infectives and are listed under their respective categories. The medicines used in tuberculosis-prevention regimens (preventive INH for latent tuberculosis, the 12-week rifapentine-isoniazid combination) are anti-infectives but their indication is prophylaxis rather than treatment of established disease. The intravenous immunoglobulin preparations have anti-infective effect in selected severe infections but their primary classification is as immunomodulators. The bacteriophage preparations under development as anti-infective alternatives to small-molecule antibacterials are mentioned on the antibacterials page for context but are not collected here as a separate category.

This category page is an encyclopedia article about its subject. The actual index of medicines belonging to the category is generated automatically by the wiki engine, from category-membership declarations on the individual medicine pages, and appears at the foot of the page below the references.