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creation date: 2025-06-14 17:27
tags: Pharmacology Incomplete

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Antibiotics

Inhibit cell wall synthesis

ß-lactams

Inhibits peptidoglycan cross-links in bacterial cell walls by binding to penicillin-binding proteins; bactericidal.

Penicillins

Natural penicillins

Clinical uses:

• Gram-positive aerobes (esp. Streptococcus pyogenes, Streptococcus pneumoniae)
• Gram-negative cocci (esp. Neisseria meningitidis)
• Spirochetes (esp. Treponema pallidum)
• Branching gram-positive anaerobes (esp. Actinomyces)

Adverse effects:

• Hypersensitivity
• Hemolytic anemia
• Drug-induced interstitial nephritis
• Seizures

Examples:

• Penicillin G (benzylpenicillin) - IV or IM due to acid lability
  • Benzathine benzylpenicillin - long acting IM; for prophylaxis against rheumatic fever
• Penicillin V (phenoxymethylpenicillin) - PO

Penicillinase-resistant penicillins

Special characteristics:

• Intrinsically ß-lactamase resistance through bulky side chains

Clinical uses:

• Narrow spectrum
• Gram-positive aerobes (especially MSSA)

Adverse effects:

• Hypersensitivity
• Interstitial nephritis

Examples:

• Nafcillin
• Dicloxacillin
• Oxacillin
• Floxacillin
• Methicillin

Aminopenicillins

Special characteristics:

• Susceptible to degradation by ß-lactamase
• Can be potentiated with a ß-lactamase inhibitor

Clinical uses:

• Broad spectrum
• Gram-positive aerobes
• Gram-negative rods (not Enterobacter spp.)
• Most effective: H. pylori, H. influenzae, E. coli, Listeria monocytogenes, Proteus mirabilis, Salmonella, Shigella, Enterococci, Spirochetes

Adverse effects:

• Hypersensitivity
• Diarrhea
• Pseudomembranous colitis
• Drug-induced rash

Examples:

• Amoxicillin (± clavulanate) - PO or IV
• Ampicillin (± sulbactam) - IV or IM

Antipseudomonal penicillins

Clinical uses:

• Broad spectrum
• Ggram-negative rods, especially Pseudomonas
• Anerobes
• Gram-positive aerobes

Adverse effects:

• Hypersensitivity

Examples:

• Piperacillin (± tazobactam) - IV
• Ticarcillin - IV
• Carbenicillin - PO

Cephalosporins

Special characteristics:

• Less susceptible to penicillinases

Adverse effects:

• Cross reactivity to penicillin allergies
• Autoimmune hemolytic anemia
• Vitamin K deficiency
• Disulfiram-like reaction
• Increased nephrotoxicity of aminoglycosides when co-administered
• Neurotoxicity
• Hyperbilirubinemia in neonates (ceftriaxone)

1st generation

Clinical uses:

• Gram-positive bacteria
• Gram-negative: Proteus mirabilis, E. coli, Klebsiella pneumoniae
• No coverage against: Listeria, Atypicals (Chalmydia, Mycoplasma, Legionella), MRSA, Enterococcus
• Perioperative wound infection prophylaxis (cefazolin)

Examples:

• Cephalexin (Keflex) PO
• Cefazolin (Ancef) IV or IM

2nd generation

Clinical uses:

• Gram-positive bacteria (less active than 1st gen)
• Gram-negative: 1st gen and H. influenzae, Klebsiella aerogenes, Neisseria, Serratia marcescens
• No coverage against: Listeria, Atypicals (Chalmydia, Mycoplasma, Legionella), MRSA, Enterococcus

Examples:

• Cefaclor PO
• Cefoxitin IV
• Cefuroxime PO or IV
• Cefotetan IV

3rd generation

Clinical uses:

• Gram-positive bacteria (worse of all cephalosporins)
• Gram-negative bacteria (broad)
• No coverage against: Listeria, Atypicals (Chalmydia, Mycoplasma, Legionella), MRSA, Enterococcus
• Pseudomonas coverage (ceftazidime and cefoperazone)
• Perioperative wound infection prophylaxis
• Meningitis treatment (ceftriaxone; good CNS penetrance)
• Gonorrhea and disseminated lyme disease (ceftriaxone)

Examples:

• Cefixime PO
• Cefpodoxime PO
• Cefdinir PO
• Ceftriaxone IV or IM
• Cefotaxmine IV
• Ceftazidime IV

4th generation

Clinical uses:

• Broad spectrum
• No coverage against: Listeria, Atypicals (Chalmydia, Mycoplasma, Legionella), MRSA, Enterococcus
• Pseudomonas coverage
• Severe life-threatening infections

Examples:

• Cefepime IV

5th generation

Clinical uses:

• Broad spectrum
• No coverage against: Atypicals (Chalmydia, Mycoplasma, Legionella), Enterococcus (except E. faecalis)
• Pseudomonas, Listeria, and MRSA coverage

Examples:

• Ceftaroline IV (US only)

Carbapenems

Special characteristics:

• Intrinsic ß-lactamase resistance

Clinical use:

• Often used as last-resort due to significant adverse effects
• Reserved for known resistant organisms
• Broad spectrum (except MRSA, and E. faecali and E. faecium)
• Pseudomonas coverage except ertapenem

Adverse effects:

• Secondary fungal infections
• CNS toxicity (seizures)
• GI upset
• Rash
• Thromboplebitis

Examples:

• Imipenem with cilastatin (dehydropeptidase I inhibitor to stop imipenem break down) IV
• Meropenem IV
• Ertapenem IV
• Doripenem IV

Monobactams

Special characteristics:

• Less susceptible to ß-lactamases

Clinical use:

• Gram-negative bacteria only
• No cross-sensitivity with penicillins
• Synergistic to aminoglycosides (alternative if renal insufficiency)
• Can combine with vancomycin or clindamycin for broad-spectrum coverage

Adverse effects: (rare)

• GI upset
• Rash

Examples:

• Aztreonam IV

Glycopeptides

Inhibits peptidoglycan synthesis by binding to D-alanyl-D-alanine section of peptidoglycan precursor; bactericidal except against C. difficile (bacteriostatic).

Special characteristics:

• CNS penetration only when meningeal vessels have increased permeability (ie. meningeal inflammation)

Clinical use:

• Gram-positive bacteria only
• Particularly useful against MDR organisms
• MRSA
• S. epidermidis
• Enterococci
• C. difficile (treated PO)

Adverse effects (IV):

• Nephrotoxicity
• Ototoxicity/vestibular toxicity
• Vancomycin flushing reaction (anaphylactoid reaction from rapid infusion) - prevent with slow rate of infusion and pretreatment with antihistamines
• Drug reaction with eosinophilia and systemic symptoms (DRESS) syndrome
• Neutropenia

Adverse effects (PO):

• Dysgeusia
• GI side effects

Examples:

• Vancomycin PO or IV
• Teicoplanin PO or IV
• Bacitracin topical

Epoxides

Disrupts peptidoglycan synthesis by inactivating enolpyruvate transferase; bactericidal.

Clinical use:

• Uncomplicated UTI due to E. coli or E. faecalis

Adverse effects:

• Mild electrolyte imbalances
• Diarrhea

Examples:

• Fosfomycin PO or IV

Disrupt cell membrane integrity

Lipopeptides

Depolarizes cell membrane by forming ion-conducting channels when lipid portion of antibiotic binds to bacterial cytoplasmic membrane; bactericidal.

Clinical use:

• Gram-positive bacteria
• S. aureus, especially MRSA
• Primarily used in skin infection, bacteremia, and endocarditis
• Vancomycin-resistant Enterococci
• Not used for pneumonia due to inactivation by surfactant

Adverse effects:

• Reversible myopathy
• Rhabdomyolysis
• Allergic pneumonitis

Examples:

• Daptomycin

Polymyxins

Causes bacterial lysis via increased permeability when cationic detergents (polypeptides) bind to outer cell membrane (phospholipids). Reduces bacterial endotoxin effect by binding and inhibiting to lipopolysaccharides; bactericidal.

Clinical use:

• Severe infections of gram-negative bacteria with MDR
• Polymyxin B used with bacitracin and neomycin for triple antibiotic ointment for superficial skin infections
• Disinfect bowel to prevent ICU infection using PO polymyxin (poor PO absorption)

Adverse effects:

• Nephrotoxicity - cautious use in renal dysfunction
• Neurotoxicity
• Urticaria, eosinophilia, and/or anaphylactoid reactions
• Respiratory failure

Examples:

• Polymyxin B IV or IM or ointment
• Polymyxin E (colistin) IV or IM

Inhibit protein synthesis (30S)

Aminoglycosides

Causes protein mistranslation by inhibiting initiation complex; bactericidal.

Special characteristics:

• Synergistic with ß-lactams as they enable aminoglycoside uptake

Clinical use:

• Severe gram-negative rods
• Ineffective against anaerobes
• PO gut prep with neomycin PO
• Second-line treatment for Mycobacterium tuberculosis and M. avium-intracellulare with Streptomycin

Adverse effects:

• Nephrotoxicity
• Ototoxicity and vestibulotoxicity (tinnitus, ataxia, vertigo)
• Neuromuscular blockade
• Teratogenicity

Contraindications:

• Myasthenia gravis
• Botulism
• Pregnancy

Examples:

• Gentamicin IV or IM
• Amikacin IV or IM
• Tobramycin IV or IM
• Streptomycin IV or IM
• Neomycin PO
• Capreomycin
• Kanamycin

Tetracyclines

Inhibits protein synthesis by blocking incoming tRNA to acceptor site; bacteriostatic.

Special characteristics:

• Poor CNS penetrance but accumulates intracellularly
• Avoid large amount of Ca2+, Mg2+, Fe2+ when taking as divalent cations inhibit absorption

Clinical use:

• Bacteria that lack a cell wall (eg. Mycoplasma pneumoniae, Ureaplasma)
• Intracellular bacteria (eg. Rickettsia, Chlamydia, Anaplasma)
• Coverage for: Borrelia burgdorferi (Lyme disease pathogen), Ehrlichia (tick-borne), Vibrio cholerae (causes cholera), Francisella tularensis (tick-borne)
• Cutibacterium acnes using doxycycline PO
• MRSA using doxycycline

Adverse effects:

• Hepatotoxicity
• Deposition in bones/teeth can inhibit bone growth in children and discolour teeth
• Damage to mucous membranes
• Photosensitivity (can cause inflammation of skin)
• Associated with Fanconi syndrome
• Rare: pseudotumour cerebri

Contraindications:

• Children <8 years of age (except doxycycline)
• Pregnancy and/or breastfeeding
• Renal failure (except doxycycline)

Examples:

• Minocycline PO or IV
• Tetracycline PO or IV
• Doxycycline PO
• Demeclocycline PO

Glycylcyclines

Inhibits protein synthesis by blocking incoming tRNA; bacteriostatic.

Special characteristics:

• Derivative of tetracycline but counters resistance mechanism of tetracyclines by preventing efflux
• Avoid taking with divalent cations

Clinical use:

• Gram-positive aerobes
• Partial against gram-negative aerobes
• MRSA and VRE
• Broad-spectrum anaerobes
• Gram-intermediate (Borrelia, mycoplasma, Rickettsia, Chlamydia)
• Deep tissue infections (good soft tissue penetration)

Adverse effects:

• GI upset
• Hepatotoxicity
• Deposition in bones and teeth
• Photosensitivity

Contraindication:

• Children <8 years
• Pregnancy and breastfeeding

Examples:

• Tigecycline IV

Inhibit protein synthesis (50S)

Macrolides

Inhibits protein synthesis by binding to 23S rRNA and inhibiting transpeptidation, translocation, and chain elongation; bacteriostatic.

Clinical use:

• Atypical pneumonia (Mycoplasma pneumoniae, Legionella pneumoniae, Chlamydia pneumoniae)
• Bordetella pertussis
• Chlamydia STI
• Gram-positive cocci (esp. Streptococcal infection w/ penicillin allergy)
• Neisseria meningitidis (2nd line prophylaxis) and Neisseria gonorrhoeae (dual therapy: ceftriaxone and azithromycin)
• Mycobacterium avium prophylaxis (azithromycin) and treatment (azithromycin or clarithromycin)
• H. pylori triple therapy (clarithromycin)

Adverse effects:

• GI upset from motility increase
• QT-interval prolongation
• Acute cholestatic hepatitis
• Rash
• Increased risk of hypertrophic pyloric stenosis (erythromycin and azithromycin) in infants <6wk age

Contraindications:

• Pregnancy

• Hepatic failure (azithromycin and clarithromycin)

• Possible risk with children <12 years (erythromycin), <6 months (clarithromycin and azithromycin)

• Erythromycin enhances effects of oral anticoagulants

• Erythromycin and clarithromycins are CYP3A4 inhibitors

Examples:

• Erythromycin PO or IV
• Azithromycin PO or IV
• Clarithromycin PO or IV
• Roxithromycin PO

Lincosamides

Inhibits protein synthesis by impairing transpeptidation; bacteriostatic.

Special characteristics:

• May have cross-resistance with macrolides

Clinical use:

• Anaerobes for aspiration pneumonia, lung abscesses, oral infections
• Group A streptococcus
• Partially effective: gram-positive aerobes including MRSA

Adverse effects:

• GI upset (including C. difficile)
• Pseudomembranous colitis
• Fever
• Teratogenicity

Contraindications:

• First trimester pregnancy and breastfeeding

Examples:

• Clindamycin

Streptogramins

Inhibits protein synthesis by inhibition of polypeptide elongation; bactericidal when in combination, bacteriostatic when separate.

Special characteristics:

• Synergistic when used together in below example

Clinical use:

• Skin and skin structure infection of S. aureus (MSSA and MRSA), S. pyogenes, Vancomycin-resistant E. faecium (but not E. faecalis)

Adverse effects:

• Nausea, vomiting
• Diarrhea
• Headache
• Myalgia, arthralgia
• Thrombophlebitis
• Rash and pruritus
• Pseudomembranous colitis

Contraindications:

• Possible risk in pregnant/breastfeeding women and children <16 years of age

Examples:

• Quinupristin-dalfopristin IV

Oxazolidinones

Inhibits protein synthesis by prevention of association of 50S and 30S subunits; bacteriostatic except against Streptococci (bactericidal).

Clinical use:

• MRSA
• VRE

Adverse effects:

• GI upset
• Pancytopenia due to bone marrow suppression
• Peripheral neuropathy
• Serotonin syndrome due to inhibition of monoamine oxidase

Contraindications:

• Concurrent use with MAOIs and SSRIs

Examples:

• Linezolid

Amphenicols

Inhibits protein synthesis by preventing tRNA from binding; bacteriostatic unless in high concentration (bactericidal).

Special characteristics:

• Not used in Canada due to side effects; may be used in lower resource countries

Examples:

• Chloramphenicol

Inhibit protein synthesis (general)

Reduction by bacterial nitroreductases to reactive metabolites which bind to ribosomes; bactericidal

Nitrofurans

Clinical use:

Urinary tract bacterias:

• Gram-positive: Enterococci, Staphylcoccus saprophyticus, group B streptococcus, Staphylococcus aureus, Staphylococcus epidermidis
• Gram-negative: E. coli, Enterobacter, Shigella, Salmonella, Citrobacter, Neisseria, Bacteroides, Klebsiella

Not effective for Pseudomonas or Proteus. Not used for pyelonephritis due to poor penetration of renal tissue.

Adverse effects:

• Nitrofurantoin-induced lung disease (NILD):
  • Acute: hypersensitivity approx. 9 days post exposure (fever, cough, rash, dyspnea)
  • Chronic: toxic reaction 6 months after initiation (cough and dyspnea that can lead to pulmonary fibrosis)
• GI upset
• Hemolytic anemia in patients with G6PD deficiency

Contraindications:

• Children <1 month of age
• Breastfeeding women or women at 38-42 week gestation
• Hepatic dysfunction
• Renal dysfunction with creatinine clearance <60 mL/min

Examples:

• Nitrofurantoin PO

Inhibit DNA gyrase

Fluoroquinolones

Inhibits DNA synthesis by inhibiting prokaryotic topoisomerase II (DNA gyrase) and topoisomerase IV; bacteriostatic and bactericidal.

Special characteristics:

• Absorption reduced when administered with polyvalent cations

Adverse effects:

• GI upset

• Neurological symptoms (eg. headache, peripheral neuropathy, seizure threshold - especially with NSAID use)

• Hyperglycemia/hypoglycemia

• QT prolongation

• Photosensitivity

• Skin rash

• Superinfection

• Life threatening exacerbation of myasthenia gravis

• Damange to growing cartilage

• Muscle ache, leg cramps, tendinitis

• Tendon rupture (esp. Achilles tendon)

• Inhibition of cytochrome P450 (ciprofloxacin)

Contraindications:

• Age <18 years (except for complicated UTI)
• Age >60 years
• Patients taking corticosteroids
• Pregnant or breastfeeding women
• Epilepsy, stroke, CNS lesions/inflammation
• QT prolongation
• Myasthenia gravis
• Cautious use in patients with renal or hepatic failure, antacid use, known aortic aneurysm or at risk of aneurysms

1st generation

Clinical use:

• Not available for use

Examples:

• Nalidixic acid PO

2nd generation

Clinical use:

• Gram-negative rods for urinary and GI infections
• Some gram-positive pathogens
• GU infections caused by Neisseria gonorrhoeae, Chlamydia trachomatis, and Ureaplasma urealyticum
• Pseudomonas aeruginosa (ciprofloxacin)

Examples:

• Norfloxacin PO
• Ciprofloxacin PO
• Ofloxacin PO

3rd generation

Clinical use:

• Atypical bacterial (eg. Leionella, Mycoplasma, Chlamydia)
• Anaerobes

Examples:

• Levofloxacin PO or IV

4th generation

Clinical use:

• Atypical bacterial (eg. Leionella, Mycoplasma, Chlamydia)
• Anaerobes
• Penicillin-resistant pneumococci (gemifloxacin)
• 2nd-line tx of tuberculosis (moxifloxacin)

Examples:

• Moxifloxacin PO
• Gemifloxacin PO
• Gatifloxacin eye drops

Disrupt DNA integrity

Nitroimidazoles

Causes single-strand breaks in DNA via free radical formation; bactericidal and antiprotozoal.

Clinical use:

• Certain protozoa (eg. Entamoeba histolytica, Giardia, Trichomonas)
• Anaerobes (eg. C. difficile, Bacteroides spp.)
• Facultative anaeobes (eg. Gardnerella vaginalis, H. pylori in place of amoxicillin for triple therapy)

Adverse effects:

• Headache
• Possible disulfiram-like reaction (evidence shows no association)
• Metallic taste and GI side effects
• Peripheral neuropathy with prolonged use

Contraindications:

• Pregnant and breastfeeding women
• Chidlren

Examples

• Metronidazole PO or IV
• Tinidazole PO or IV

Inhibit folic acid synthesis

Sulfonamides and diaminopyrimidines

Prevents production of bacterial tetrahydrofolate (downstream inhibition of DNA methylation). Sulfonamides inhibit dihydropteroate synthetase and diaminopyrimidines inhibit dihydrofolate reductase; bactericidal and bacteriostatic, respectively.

Clinical use:

• UTI and acute otitis media
• Sulfisoxazole:
  • Gram-positive and gram-negative bacteria
  • N. meningitidis
  • Chlamydia trachomatis
  • Nocardia asteroides
  • Toxoplasma gondii
  • Plasmodia spp.
• Septra:
  • Shigella
  • Salmonella
  • Empiric treatment for simple UTI
  • Prophylaxis of P. jirovecii
  • Prophylaxis of toxoplasmosis

Adverse effects:

Sulfonamides:

• CYP450 inhibition (drug interactions)
• Displacement of drugs from albumin (eg. warfarin)
• Kernicterus in infancy
• Nephrotoxicity
• GI upset
• Hyperkalemia
• Agranulocytosis
• Aplastic anemia, thrombocytopenia, pancytopenia
• Hemolytic anemia in patients with G6PD deficiency
• Photosensitivity
• Fever
  Diaminopyrimidine derivatives:
• Megaloblastic anemia
• Leukopenia, granulocytopenia
• Hyperkalemia
• Increased creatinine

Examples:

• Sulfamethoxazole-trimethoprim (Septra) PO or IV
• Sulfadiazine PO with pyrimethamine PO
• Sulfisoxazole PO

Antimycobacterials

Inhibits DNA, RNA, cell wall, and protein synthesis by binding to bacterial ribosomes; bacteriostatic except at higher concentrations (bactericidal).

Rifamycins

Inhibits protein synthesis by blocking mRNA synthesis through inhibition of RNA-polymerase; bacteriostatic and bactericidal.

Special characteristics:

Clinical use:

• Tuberculosis treatment

Adverse effects:

Contraindications:

Examples:

Hydrazides

Inhibits cell wall synthesis by inhibiting mycolic acid synthesis; bactericidal.

Special characteristics:

Clinical use:

Adverse effects:

Contraindications:

Examples:

Nicotinamides

Uncertain mechanism; bacteriostatic to bactericidal depending on concentration.

Special characteristics:

Clinical use:

Adverse effects:

Contraindications:

Examples:

Ethylenediamine derivates

Inhibits cell wall synthesis by inhibiting arabinosyltransferase; bacteriostatic.

Special characteristics:

Clinical use:

Adverse effects:

Contraindications:

Examples:

Sulfones

Inhibits dihydrofolic acid synthesis by competitive antagonism of para-aminobenzoic acid; bacteriostatic and bactericidal.

Special characteristics:

Clinical use:

Adverse effects:

Contraindications:

Examples: