Common Antibiotic Classes and Uses

Bacteria that stain blue in a Gram stain, and have a thick cell wall.

Bacteria that stain red in a Gram stain, and have a thin cell wall with lipopolysaccharides.

Lowest drug concentration that stops bacterial growth after incubation.

Lowest drug concentration that kills 99.9% of bacteria.

Range of bacteria an antibiotic affects.

A class of antibiotics derived from mold that are bactericidal (kill bacteria) and work by inhibiting cell wall synthesis.

Penicillins inhibit the transpeptidase enzyme, preventing the cross-linking of peptidoglycan molecules in the bacterial cell wall. This weakens the cell wall, causing increased osmotic pressure and eventually cell lysis.

Penicillin V and Penicillin G are narrow-spectrum antibiotics effective against common gram-positive organisms, such as those causing ear and throat infections.

Some bacteria produce penicillinase, an enzyme that breaks down penicillin. Cloxacillin is a penicillinase-resistant penicillin used for staph aureus infections.

Aminopenicillins like Ampicillin, Amoxicillin, Bacampicillin, and Pivampicillin are considered broad spectrum, effective against both gram-positive and gram-negative organisms.

Amoxicillin is often combined with clavulanic acid, a beta-lactamase inhibitor, to overcome bacterial resistance and increase its effectiveness.

Ticarcillin, often combined with Potassium Clavulanate, has a broader spectrum than first and second-generation penicillins, including effectiveness against Pseudomonas aeruginosa.

Piperacillin, often combined with Tazobactam, has the broadest spectrum of activity, including effectiveness against Pseudomonas aeruginosa and other gram-negative bacteria.

The main goals of tuberculosis (TB) treatment are to prevent the disease from progressing, stop its spread, treat active infections, and relieve symptoms.

Healthcare workers are screened for TB to prevent the spread of the disease to patients and colleagues. They may be exposed to patients with active TB, and early detection can prevent transmission to others.

Isoniazid is a first-line drug used to prevent TB infection. It's often prescribed for people who have been exposed to TB but haven't developed the disease.

Rifampin is a powerful antibiotic specifically used to treat active tuberculosis (TB) infections. It's highly effective against the Mycobacterium tuberculosis bacteria.

Ethambutol is a TB drug that can also be used for other mycobacterial infections, not just TB.

A group of antibiotics that are effective against a wide range of gram-negative bacteria, often used for serious infections not responding to second-generation cephalosporins. They are more potent and cross the blood-brain barrier more easily, making them useful for certain types of meningitis. Examples include Cefotaxime, Cefixime, Ceftazidime, and Ceftriaxone.

A third-generation cephalosporin that is only available orally. It is effective against bronchitis, urinary tract infections, sinusitis, and otitis media, but other medications may be just as effective for these conditions.

A group of cephalosporins that have a similar spectrum of activity to third-generation antibiotics but are more resistant to beta-lactamase, an enzyme that breaks down some antibiotics.

The only fourth generation cephalosporin currently available. It has a wide spectrum of activity against both gram-positive and gram-negative bacteria.

A group of antibiotics that are bacteriostatic, meaning they prevent the growth of bacteria. They work by interfering with bacterial protein synthesis. They are active against both gram-positive and gram-negative bacteria and are commonly used for bronchitis and acne.

Tetracyclines are used as the primary choice for treating several unusual infections, including: Rocky Mountain Spotted Fever caused by Rickettsiae, Typhus, Mycoplasma pneumoniae (viral), Vibrio cholerae, Chlamydia trachomatis (urethritis), Borrelia burgdorferi (Lyme disease), and bacterial acne (Minocycline's only indication).

Common side effects of tetracyclines include nausea, vomiting, diarrhea, and photosensitivity (sunburn). They can also lead to fungal superinfections (Candida). Expired tetracyclines can cause Fanconi syndrome, a rare kidney disorder. Children under 8 years old, pregnant women, and breastfeeding mothers should avoid these medications.

When dispensing tetracyclines, it is highly recommended to advise patients to avoid calcium, dairy products, antacids, and mineral supplements within 1 hour before or 2 hours after taking their dose. Sunlight warnings, pregnancy/lactation precautions, and instructions to complete the full course of treatment should also be included.

A group of antibiotics that are bacteriostatic and inhibit protein synthesis. Their activity varies by drug but generally covers gram-positive and some gram-negative bacteria.

A macrolide that covers a similar spectrum to Penicillin V and is used to treat Legionella pneumophilia, Mycoplasma pneumoniae, and Chlamydia trachomatis.

A macrolide that has a similar spectrum to Erythromycin. Azithromycin is often favored due to once-daily dosing and good tissue penetration.

Type of bacteria commonly found in the stomach that can cause ulcers and gastritis.

Fluoroquinolones should not be taken with minerals like calcium, aluminum, magnesium, or iron as these minerals reduce the antibiotic's absorption.

Norfloxacin (a fluoroquinolone used for urinary tract infections) should be taken on an empty stomach because food interferes with its absorption.

An antibiotic used specifically for urinary tract infections and cystitis. Its mechanism of action involves interfering with bacterial protein synthesis, cell wall synthesis, and DNA/RNA synthesis.

Nitrofurantoin may cause gastrointestinal intolerance (nausea, vomiting) and pulmonary reactions (fibrosis, pneumonitis), especially with long-term use.

Vancomycin is used intravenously for serious gram-positive infections and orally for Clostridium difficile infections.

Vancomycin can cause ototoxicity, nephrotoxicity, and flushing (red man syndrome) – an allergic reaction caused by rapid infusion.

Prescribers choose antibiotics based on guidelines, bacterial identification, antibiotic susceptibility (spectrum), and the risk of prescribing the wrong agent.

Pharmacists play a crucial role in dispensing antibiotics accurately, performing reconstitutions, ensuring proper labeling, verifying insurance coverage, and ensuring the drug is appropriate for the patient's needs.

Primarily gastrointestinal side effects like nausea, vomiting, and diarrhea. Erythromycin especially has dose-related adverse effects.

A lincosamide antibiotic effective against Gram-positive and anaerobic bacteria. Available in various forms for oral, topical, and injection administration.

Diarrhea due to Clostridium difficile overgrowth, leading to pseudomembranous colitis. Symptoms include severe abdominal cramps. Can occur with oral or IV administration.

Bactericidal antibiotics targeting Gram-negative bacilli. They work by inhibiting bacterial protein synthesis at the ribosome. Examples include Gentamicin, Tobramycin, Amikacin, and Streptomycin.

Poorly absorbed through the GI tract. Primarily given IV or IM for systemic effect. Topical preparations exist for ocular and otic infections.

Synthetic antibiotics that competitively inhibit PABA, a compound needed by bacteria for folic acid production. This inhibits bacterial growth, making them bacteriostatic.

A combination drug containing sulfamethoxazole and trimethoprim. Both components interfere with folic acid synthesis in bacteria, creating a synergistic effect.

Commonly used for respiratory, urinary, GI, and otitis media infections in both children and adults. Preferred treatment and prophylaxis for Pneumocystis jirovecii pneumonia.

GI intolerance (N/V/D), crystalluria (rare with hydration), photosensitivity, and allergic reactions like pruritis, rashes, and rarely Stevens-Johnson Syndrome.

Sulfonamides are highly protein-bound drugs, increasing free concentrations of other highly bound drugs like anticoagulants and hyperglycemic drugs.

Synthetic, broad-spectrum antibiotics that inhibit bacterial DNA gyrase, an enzyme essential for replication. They are bactericidal.

A commonly used fluoroquinolone for urinary, respiratory, skin, soft tissue, bone, and GI infections. Available in various strengths and dosage forms.

Considered 'respiratory fluoroquinolones' due to effectiveness in respiratory infections.

Common side effects include headache, dizziness, GI disturbance, rash, photosensitivity, and joint swelling. Cartilage defects reported in animal studies.