Antibiotics, Powerful Action, History, Types, Uses, Side effects and top 10 Brands

Introduction

Antibiotic drugs, commonly known as antibiotics, are powerful medicines designed to fight bacterial infections. They work either by killing bacteria or inhibiting their growth. These drugs are used to treat certain bacterial infections, such as strep throat, urinary tract infections, and E. coli.

They are available in various forms, including pills, capsules, liquids, creams, sprays, ointments, eye ointments, eye drops, ear drops, and through injections or intravenously (IV), which are usually for more serious infections.

Etymology

The term “antibiosis,” meaning “against life,” was introduced to describe the phenomenon exhibited by early antibacterial drugs. Initially observed in bacteria by Louis Pasteur and Robert Koch in 1877, these substances were later termed antibiotics by American microbiologist Selman Waksman in 1947. The term “antibiotic” encompasses medications that kill bacteria or inhibit their growth, irrespective of their microbial or synthetic origin. Its etymology derives from Greek roots meaning “against life” and “fit for life.”

Historical Use of Antibiotics

The use of antibiotics dates back to ancient times, with many civilizations employing topical applications of moldy bread for its beneficial effects. References to the use of mouldy bread for medicinal purposes have been found in ancient Egypt, Nubia, China, Serbia, Greece, and Rome The first person to directly document the use of molds to treat infections was John Parkinson (1567–1650).

These treatments often worked because many organisms, including many species of mold, naturally produce antibiotic substances. However, ancient practitioners could not precisely identify or isolate the active components in these organisms.

Development of Antibiotics in the 20th Century

The revolution of medicine in the 20th century was significantly influenced by the development of antibiotics. Synthetic antibiotic chemotherapy as a science and the development of antibacterials began in Germany with Paul Ehrlich in the late 1880s.

Alexander Fleming’s discovery of modern-day penicillin in 1928 and its widespread use during wartime proved significantly beneficial

Additionally, the first sulfonamide and the first systemically active antibacterial drug, Prontosil, was developed by a research team led by Gerhard Domagk in 1932 or 1933 at the Bayer Laboratories of the IG Farben conglomerate in Germany.

Impact and Challenges

The widespread use of antibiotics has profoundly impacted medicine, saving millions of lives. However, the effectiveness and easy access to antibiotics have also led to their overuse, contributing to the evolution of antibiotic-resistant bacteria

The World Health Organization has classified antimicrobial resistance as a widespread “serious threat” that can potentially affect anyone of any age in any country. Global deaths attributable to antimicrobial resistance numbered 1.27 million in 2019.

Importance of Antibiotics in Modern Medicine

Antibiotics are essential in modern healthcare. They treat a wide range of infections, from minor ailments like strep throat to life-threatening conditions such as sepsis. Beyond treating infections, It is also crucial in surgeries and chemotherapy, where they prevent and manage infections in vulnerable patients.

Types of Antibiotic Drugs

These drugs are classified based on their spectrum of activity, mechanism of action, and chemical structure. Understanding these classifications helps in selecting the appropriate antibiotic for specific infections.

Classification by Spectrum of Activity

• Broad-Spectrum Antibiotics: Effective against a wide range of bacteria, both Gram-positive and Gram-negative. Examples include tetracyclines and amoxicillin.
• Narrow-Spectrum Antibiotics: Target specific types of bacteria. For instance, penicillin G is effective mainly against Gram-positive bacteria.

Classification by Mechanism of Action

• Inhibitors of Cell Wall Synthesis: These antibiotics, such as penicillins and cephalosporins, prevent bacteria from forming cell walls, causing them to burst and die.
• Protein Synthesis Inhibitors: Antibiotics like tetracyclines and macrolides bind to bacterial ribosomes, disrupting protein production.
• Nucleic Acid Synthesis Inhibitors: Fluoroquinolones, for example, inhibit DNA replication in bacteria.
  Metabolic Pathway Inhibitors: Sulfonamides block specific metabolic pathways, essential for bacterial survival.

Classification by Chemical Structure

• Beta-Lactams: Includes penicillins, cephalosporins, carbapenems, and monobactams.
• Macrolides: Such as erythromycin and azithromycin.
• Tetracyclines: Includes doxycycline and minocycline.
• Aminoglycosides: Such as gentamicin and streptomycin.
• Quinolones: Includes ciprofloxacin and levofloxacin.

Mechanisms of Action

Antibiotics employ various mechanisms to eradicate bacteria or inhibit their growth.

Disruption of Cell Wall Synthesis

Antibiotics like penicillins and cephalosporins inhibit the synthesis of peptidoglycan, a vital component of bacterial cell walls, leading to cell lysis and death.

Inhibition of Protein Synthesis

Antibiotics such as tetracyclines and macrolides interfere with bacterial ribosomes, preventing them from synthesizing essential proteins needed for growth and replication.

Inhibition of Nucleic Acid Synthesis

Fluoroquinolones target bacterial enzymes like DNA gyrase, which are crucial for DNA replication and transcription.

Inhibition of Metabolic Pathways

Sulfonamides mimic para-aminobenzoic acid (PABA), a substrate necessary for folic acid synthesis in bacteria, thereby blocking essential metabolic pathways.

Commonly Used Antibiotics

Understanding the commonly used antibiotics helps in recognizing their uses and potential side effects.

Penicillins

Penicillins are widely used to treat infections like pneumonia, strep throat, and meningitis. They are generally safe but can cause allergic reactions in some individuals.

Cephalosporins

These are used for a variety of infections including respiratory tract infections, urinary tract infections, and skin infections. They have a similar mechanism to penicillins but a broader spectrum.

Macrolides

Macrolides like erythromycin and azithromycin are used to treat respiratory infections, skin infections, and sexually transmitted infections. They are often prescribed for patients allergic to penicillin.

Tetracyclines

Tetracyclines are effective against a wide range of infections, including acne, Lyme disease, and respiratory infections. They should not be used in children or pregnant women due to potential effects on bone growth and teeth discolouration.

Aminoglycosides

These are potent against severe infections like sepsis and hospital-acquired infections. However, they can be toxic to the kidneys and ears, requiring careful monitoring.

Fluoroquinolones

Fluoroquinolones are broad-spectrum antibiotics used for respiratory and urinary tract infections. They are associated with risks of tendonitis and tendon rupture, particularly in older adults.

Antibiotic Resistance

Antibiotic resistance is a significant public health challenge. It occurs when bacteria evolve mechanisms to resist the effects of antibiotics.

Causes of Resistance

• Overuse and Misuse of Antibiotics: Prescribing antibiotics for viral infections or not completing the prescribed course.
• Agricultural Use: Using antibiotics in livestock to promote growth, can lead to resistant bacteria entering the human food chain.
• Lack of New Antibiotics: The slow pace of new antibiotic development has not kept up with the rate of resistance.

Mechanisms of Resistance

• Enzymatic Degradation: Bacteria produce enzymes like beta-lactamases that degrade antibiotics.
• Efflux Pumps: Bacteria pump antibiotics out of their cells before they can act.
• Mutation: Genetic mutations alter the target sites of antibiotics.
• Horizontal Gene Transfer: Bacteria can acquire resistance genes from other bacteria.

Combatting Resistance

Efforts to combat antibiotic resistance include promoting responsible antibiotic use, developing new antibiotics, and implementing infection control measures in healthcare settings.

Uses

Antibiotics are powerful medications that treat certain infections and save lives when used properly. They either stop bacteria from reproducing or destroy them Here are some common uses of antibiotics:

Treating Bacterial Infections

Antibiotics are the cornerstone of treatment for various bacterial infections. They work by either killing bacteria (bactericidal) or inhibiting their growth (bacteriostatic), allowing the body’s immune system to clear the infection. Common bacterial infections treated with antibiotics include:

• Skin Infections: Such as cellulitis, impetigo, and folliculitis.
• Chest Infections: Including pneumonia and bronchitis.
• Urinary Tract Infections (UTIs): Infections affecting the bladder, urethra, or kidneys.
• Sexually Transmitted Infections (STIs): Antibiotics are used to treat bacterial STIs like chlamydia, gonorrhea, and syphilis.

Preventing Bacterial Infections

This drug is used prophylactically to prevent infections, particularly in high-risk situations. This proactive approach is common in scenarios such as:

• Surgical Prophylaxis: Antibiotics are administered before surgery to prevent surgical site infections.
• Preventing Endocarditis: Antibiotic drugs may be given before dental procedures to prevent bacterial endocarditis in individuals with certain heart conditions.

Treating Specific Conditions

Antibiotic drugs are employed to address various specific conditions beyond traditional infections:

• Bladder Infections: Antibiotics such as nitrofurantoin or trimethoprim-sulfamethoxazole are commonly used to treat urinary tract infections affecting the bladder.
• Head Lice: Topical antibiotics like permethrin are used to treat infestations of head lice.
• Skin Conditions: Antibiotic drugs are prescribed for skin conditions caused by bacteria, including acne vulgaris, rosacea, erythrasma, and pityriasis lichenoides.

Empiric Therapy

In cases where an exact diagnosis is not immediately available, antibiotic drugs are sometimes prescribed empirically based on clinical symptoms. This approach, known as empiric therapy, allows for the timely initiation of treatment before microbiological results are obtained.

Routes of Administration

Antibiotic drugs can be administered through various routes depending on the severity and location of the infection. The different routes of administration for antibiotic treatment include:

Oral Administration

Antibiotic drugs are usually taken by mouth in the form of pills, capsules, or liquids. This is the most common route of administration for antibiotics and is suitable for treating most mild to moderate infections.

Topical Administration

Topical administration involves applying antibiotics directly to the part of the body with the infection. This can be in the form of creams, lotions, sprays, or drops for skin infections, eye infections, or ear infections.

Topical antibiotic drugs are available in over-the-counter (OTC) creams and ointments and can be used for certain skin conditions, including acne and cellulitis.

Advantages of topical application include achieving high and sustained concentrations of antibiotics at the site of infection, reducing the potential for systemic absorption and toxicity, and reducing the total volumes of antibiotics required, thereby also reducing the risk of antibiotic misuse.

Injection or Intravenous Administration

In more severe cases, particularly deep-seated systemic infections, antibiotic drugs can be given intravenously or by injection. This route is usually recommended, at least initially, for severe life-threatening infections and deep-seated infections because of concerns about not achieving adequate antibiotic concentrations at the site of infection
Antibiotics can be given through an injection or intravenously (IV), which is usually for more serious infections.

Other Topical Applications

Where the site of infection is easily accessed, antibiotics may be given topically in the form of eye drops onto the conjunctiva for conjunctivitis or ear drops for ear infections and acute cases of swimmer’s ear.

Missing a Dose

If you forget to take a dose of your antibiotics, here’s what you should do:

• Check the Patient Information Leaflet: Review the information leaflet that came with your medicine to find out what to do in case of a missed dose.
• Consult a Healthcare Professional: If you’re unsure about what to do, it’s best to speak to a pharmacist or a General Practitioner (GP) for guidance.
• Take the Missed Dose: In most cases, you can take the missed dose as soon as you remember and then continue with your regular dosing schedule. However, if it’s almost time for the next dose, it’s advised to skip the missed dose and continue with the regular dosing schedule. Do not take a double dose to make up for the missed one.

Accidentally Taking an Extra Dose

If you accidentally take an extra dose of your antibiotic:

• Increased Risk of Side Effects: There’s an increased risk of experiencing side effects if you take 2 doses closer together than recommended.
• Unlikely Serious Harm: Accidentally taking one extra dose of your antibiotic is unlikely to cause serious harm, but it can increase the chances of getting side effects such as stomach pain, diarrhea, and nausea.
• Seek Medical Advice: If you accidentally take more than one extra dose of your antibiotic, experience severe side effects, or are worried, it’s important to speak to your GP or call NHS 111 (in the UK) as soon as possible for guidance and medical advice.

Production of Antibiotics

Antibiotic drugs are medications that combat bacterial infections, and their production involves various methods.

Natural Compounds and Synthesis

Modern antibiotics are often semisynthetic modifications of natural compounds. For example, beta-lactam antibiotics like penicillins are produced by fungi in the genus Penicillium. Some antibiotic drugs, such as aminoglycosides, are still isolated directly from living organisms. However, others, like sulfonamides, quinolones, and oxazolidinones, are entirely synthesized through chemical processes.

Production Process

After screening antibiotics against various bacteria, the production of the active compounds occurs through fermentation. This process typically takes place in environments with high levels of oxygen, fostering the growth of bacteria necessary for antibiotic production

Side Effects

While antibiotics are generally safe, they can cause side effects ranging from mild to severe.

Common Side Effects

• Gastrointestinal Issues: Nausea, vomiting, diarrhoea, and abdominal pain.
• Allergic Reactions: Rashes, itching, and anaphylaxis in severe cases.
• Photosensitivity: Increased sensitivity to sunlight, leading to sunburns.
• Disruption of Normal Flora: Antibiotics can disrupt the balance of normal bacteria in the gut, leading to infections like Clostridioides difficile.

Severe Side Effects

• Tendon Damage: Associated with fluoroquinolones.
• Kidney and Liver Toxicity: Particularly with aminoglycosides.
• Hematologic Effects: Rare cases of anaemia or low white blood cell counts.

Considerations and Interactions

1. Medical Conditions and Special Populations

Some antibiotics may not be suitable for individuals with certain medical conditions, or for women who are pregnant or breastfeeding. It is crucial to inform your healthcare professional if you are pregnant or breastfeeding so they can prescribe the most appropriate antibiotic for your situation.

2. Personalized Prescription

Only take antibiotics that have been specifically prescribed for you. Do not use antibiotics prescribed for someone else, as this can lead to inappropriate treatment and potential side effects.

3. Medication Interactions

Antibiotic drugs can interact with other medications, potentially reducing their effectiveness or increasing the risk of adverse effects.

Notable interactions include:

Contraceptive Pill: Some antibiotics may reduce the effectiveness of oral contraceptives.
Alcohol: Consuming alcohol with certain antibiotics can cause severe reactions and side effects.

4. Reading Information Leaflet:

Carefully read the patient information leaflet that accompanies your antibiotic medication. This leaflet provides essential details on usage, potential side effects, and interactions with other substances.

Antibiotics During Pregnancy

Antibiotic drugs are commonly prescribed during pregnancy, but the choice of medication must be made carefully. The safety of antibiotics during pregnancy depends on several factors, including the type of antibiotic, the timing during pregnancy, the dosage, and the duration of treatment.

Safe Antibiotics During Pregnancy

• Penicillins: Includes amoxicillin (Amoxil, Larotid) and ampicillin.
• Cephalosporins: Includes cefaclor and cephalexin (Keflex).
• Clindamycin: (Cleocin, Clinda-Derm, Clindagel).

Antibiotic Drugs to Avoid During Pregnancy

• Tetracyclines: Can affect bone development and discolour a developing baby’s teeth. These are not recommended after the fifth week of pregnancy.
• Sulfonamides: Might pose risks such as heart conditions, cleft lip or palate, and jaundice. These are generally avoided during the first trimester and near delivery.

If an antibiotic is necessary to treat your condition during pregnancy, your doctor will prescribe the safest option and appropriate dosage. Always discuss any questions or concerns about antibiotic use during pregnancy with your doctor to ensure the best care for you and your baby.

Top 10 Generic Antibiotics

1. Amoxicillin
2. Doxycycline
3. Cephalexin
4. Ciprofloxacin
5. Clindamycin
6. Metronidazole
7. Azithromycin
8. Sulfamethoxazole and Trimethoprim
9. Amoxicillin and Clavulanate
10. Levofloxacin

Top 10 Brand Names of Antibiotics

1. Augmentin
2. Flagyl
3. Amoxil
4. Velosef
5. Keflex
6. Oxidil
7. Novidat
8. Calamox
9. Avelox
10. Cicatrin

Top 10 Antibiotic Classes 

1. Penicillins
2. Tetracyclines
3. Cephalosporins
4. Quinolones
5. Lincomycins
6. Macrolides
7. Sulfonamides
8. Glycopeptides
9. Aminoglycosides
10. Carbapenems

Additional Information

Antibiotic drugs are crucial medications used to treat bacterial infections by killing bacteria or inhibiting their growth. They do not work against viruses. The misuse and overuse of antibiotics have led to the rise of antibiotic-resistant bacteria, posing a major public health threat. To prevent resistance, antibiotics should be used responsibly by following prescriptions and completing treatment courses. Ongoing research aims to develop new antibiotics and alternative therapies. Preventive measures like vaccination, good hygiene, and infection control are also vital in combating antibiotic resistance.