ANTIBIOTICS
They are a type of medication used to treat bacterial infections. They work by either killing bacteria or inhibiting their growth. Common examples include penicillin, amoxicillin, and ciprofloxacin.
It’s important to use antibiotics responsibly to avoid issues like antibiotic resistance, where bacteria evolve to become resistant to the drugs. If you have specific questions about antibiotics or need advice on their use.
Classification of antibiotics.
Antibiotics can be classified in various ways, including by their mechanism of action, chemical structure, spectrum of activity, and origin. Here’s a summary of the common classification methods:
1. By Mechanism of Action
- Cell Wall Synthesis Inhibitors: These antibiotics interfere with the synthesis of the bacterial cell wall, leading to cell lysis and death.
- Examples: Penicillins, Cephalosporins, Carbapenems, Monobactams, Glycopeptides (e.g., Vancomycin)
- Protein Synthesis Inhibitors: These target bacterial ribosomes, hindering protein production.
- Examples: Macrolides (e.g., Erythromycin), Tetracyclines, Aminoglycosides (e.g., Gentamicin), Chloramphenicol, Clindamycin
- Nucleic Acid Synthesis Inhibitors: These interfere with DNA or RNA synthesis.
- Examples: Quinolones (e.g., Ciprofloxacin), Rifamycins (e.g., Rifampicin), Metronidazole
- Metabolic Pathway Inhibitors: These block bacterial metabolic pathways essential for survival.
- Examples: Sulfonamides, Trimethoprim (often used together as co-trimoxazole)
- Cell Membrane Disruptors: These antibiotics disrupt the bacterial cell membrane, causing cell death.
- Examples: Polymyxins (e.g., Polymyxin B, Colistin), Daptomycin
2. By Chemical Structure
- Beta-lactams: Contain a beta-lactam ring.
- Examples: Penicillins, Cephalosporins, Carbapenems, Monobactams
- Aminoglycosides: Contain amino sugars linked by glycosidic bonds.
- Examples: Gentamicin, Streptomycin, Amikacin
- Tetracyclines: Characterized by a four-ring structure.
- Examples: Tetracycline, Doxycycline
- Macrolides: Contain a macrocyclic lactone ring.
- Examples: Erythromycin, Azithromycin, Clarithromycin
- Quinolones/Fluoroquinolones: Contain a quinolone core structure.
- Examples: Ciprofloxacin, Levofloxacin
3. By Spectrum of Activity
- Broad-spectrum antibiotics: Effective against a wide range of bacteria, including both Gram-positive and Gram-negative bacteria.
- Examples: Tetracyclines, Chloramphenicol, Carbapenems, Fluoroquinolones
- Narrow-spectrum antibiotics: Effective against a specific group of bacteria.
- Examples: Penicillin G (mostly Gram-positive bacteria), Vancomycin (Gram-positive cocci)
4. By Origin
- Natural antibiotics: Directly derived from natural sources like fungi or bacteria.
- Examples: Penicillin (from Penicillium mold), Streptomycin (from Streptomyces bacteria)
- Semi-synthetic antibiotics: Chemically modified derivatives of natural antibiotics.
- Examples: Amoxicillin, Cephalexin
- Synthetic antibiotics: Entirely man-made through chemical processes.
- Examples: Sulfonamides, Fluoroquinolones
5. By Bacterial Target
- Gram-positive bacteria: Antibiotics primarily effective against Gram-positive bacteria.
- Examples: Penicillin, Vancomycin
- Gram-negative bacteria: Antibiotics primarily effective against Gram-negative bacteria.
- Examples: Polymyxins, Aminoglycosides
- Mycobacteria: Antibiotics effective against mycobacteria, such as those causing tuberculosis.
- Examples: Isoniazid, Rifampicin
Each classification method provides a different perspective on how antibiotics work and are used in clinical settings.
1. Oral Antibiotics (Tablet, Capsule, Liquid)
Oral antibiotics are commonly used for mild to moderate infections and offer the convenience of self-administration. They are absorbed through the digestive tract and distributed throughout the body via the bloodstream.
Examples of Oral Antibiotics:
- Amoxicillin: Often used to treat infections like pneumonia, bronchitis, and urinary tract infections (UTIs).
- Azithromycin: Commonly prescribed for respiratory infections, skin infections, and sexually transmitted infections (STIs).
- Doxycycline: Used for a wide range of infections including acne, UTIs, and certain STIs like chlamydia.
- Ciprofloxacin: Effective against a broad range of infections, including UTIs, gastrointestinal infections, and respiratory infections.
- Cephalexin: Frequently prescribed for skin infections, respiratory tract infections, and bone infections.
- Metronidazole: Used for anaerobic bacterial infections, including certain gastrointestinal infections and infections caused by parasites.
2. Injectable Antibiotics (Intravenous, Intramuscular, Subcutaneous)
Injectable antibiotics are often reserved for more severe infections, infections in hospitalized patients, or when oral administration is not feasible. Injections can provide a higher concentration of the antibiotic in the bloodstream or targeted area more rapidly than oral forms.
Examples of Injectable Antibiotics:
- Penicillin G (Intravenous/Intramuscular): Used for severe bacterial infections, including syphilis, bacterial endocarditis, and meningitis.
- Ceftriaxone (Intravenous/Intramuscular): A broad-spectrum cephalosporin used for severe infections like meningitis, sepsis, and pneumonia.
- Vancomycin (Intravenous): Used for serious Gram-positive infections, including MRSA (Methicillin-resistant Staphylococcus aureus) and severe infections in patients allergic to beta-lactams.
- Gentamicin (Intravenous/Intramuscular): An aminoglycoside used for severe infections, particularly Gram-negative bacteria and some Gram-positive bacteria in combination therapy.
- Meropenem (Intravenous): A carbapenem used for severe or high-risk bacterial infections, including intra-abdominal infections, meningitis, and sepsis.
- Piperacillin/Tazobactam (Intravenous): A broad-spectrum antibiotic used for severe infections, including hospital-acquired infections and infections in immunocompromised patients.
Key Considerations:
- Severity of Infection: Severe infections often require injectable antibiotics for faster and more effective treatment.
- Site of Infection: Infections in areas where it’s difficult for oral antibiotics to reach may require injection (e.g., central nervous system infections).
- Patient Condition: Patients who are critically ill, cannot swallow, or have severe nausea/vomiting may need injectable forms.
- Antibiotic Resistance: Some infections caused by resistant bacteria may require specific antibiotics that are only available in injectable forms.
Switching from IV to Oral Antibiotics (IV to PO Conversion):
In some cases, patients may start treatment with injectable antibiotics in a hospital and then switch to oral antibiotics as their condition improves. This is known as an “IV to PO” conversion and is common in the management of many infections.
