ANTIBIOTICS
Antibiotics are chemical substances derived from microorganisms that either inhibit the growth of or destroy other microorganisms.
They are pivotal in combating bacterial infections and are divided into two primary categories:
- Bacteriostatic Antibiotics: Inhibit bacterial growth.
- Bactericidal Antibiotics: Directly kill bacteria.
Classification of Antibiotics
Antibiotics can be classified based on their:
- Mechanism of Action
- Spectrum of Activity
- Chemical Structure
Mechanism of Action
Spectrum of Activity
Chemical Structure
BETA-LACTAM ANTIBIOTICS
Definition: Beta-lactam antibiotics are a class of antibiotics characterized by a beta-lactam ring in their chemical structure. They primarily include:
- Penicillins
- Cephalosporins
- Carbapenems
Mechanism of Action: Beta-lactam antibiotics inhibit bacterial cell wall synthesis by targeting peptidoglycan, a crucial component that provides rigidity to bacterial cell walls. They inhibit transpeptidases, also known as penicillin-binding proteins (PBPs), which are essential for peptidoglycan synthesis.
PENICILLINS
Origin: Penicillins are derived from the fungus Penicillium chrysogenum.
Classification:
- Natural Penicillins
- Semisynthetic Penicillins
Examples:
Natural Penicillins:
- Sodium Penicillin G
- Procaine Penicillin G
- Benzathine Penicillin G
- Phenoxymethyl Penicillin (Penicillin V)
Semisynthetic Penicillins:
- Cloxacillin
- Ampicillin
- Amoxicillin
- Amoxicillin + Clavulanic Acid
Pharmacokinetics of Penicillin G
- Absorption: Destroyed by gastric acid; food interferes with absorption.
- Distribution: Therapeutic concentrations can reach the CSF in the presence of inflammation.
- Excretion: Primarily through the kidneys.
Dosage:
- Benzylpenicillin: 0.5-4 million units (MU)
- Procaine Penicillin: 0.5-2 MU
- Benzathine Penicillin: 1.2 -2.4 MU
Indications for Penicillins
- Pneumococcal Infections: Pneumonia, meningitis, osteomyelitis.
- Streptococcal Infections: Pharyngitis, sinusitis, pneumonia, endocarditis.
- Meningococcal Infections
- Other Infections: Syphilis, diphtheria, tetanus, gas gangrene, anthrax, necrotizing fasciitis, prevention of rheumatic fever, bites, and mouth infections.
Side Effects
- Allergic Reactions: Skin rashes, urticaria, fever, bronchospasm, serum sickness, anaphylaxis.
- Neurological: Confusion, muscle twitching, convulsions, coma (from large doses).
- Injection Site Reactions: Pain at the site of injection, thrombophlebitis with intravenous administration.
Drug Interactions
- Probenecid: Inhibits renal excretion of penicillins.
- Oral Contraceptives: Reduced effectiveness.
- Methotrexate: May increase toxicity due to reduced excretion.
Nursing Considerations
- Intramuscular administration of benzyl penicillin can be painful.
- Intravenous penicillin must be given separately to avoid incompatibility.
- Avoid large doses of intravenous benzyl penicillin to prevent convulsions.
- Administer benzathine penicillin as two injections at separate sites.
AMPICILLIN
Description: Ampicillin is a semisynthetic penicillin with broad-spectrum activity against both gram-positive and gram-negative bacteria.
Pharmacokinetics:
- Absorption: Poorly absorbed; food reduces its absorption.
- Distribution: Widely distributed throughout the body.
- Excretion: Primarily through the kidneys.
Dosage: 500 mg – 2 g.
Indications:
- Infections: Bronchitis, septicaemia, urinary tract infections, endocarditis, gonorrhea, acute cholecystitis, pneumonia, typhoid, meningitis, sinusitis, otitis media.
Contraindications:
- Hypersensitivity to penicillins.
- Infectious mononucleosis.
Side Effects:
- Nausea and vomiting, fever, diarrhea, rash, urticaria, antibiotic-related colitis, serum sickness-like reaction, pain at injection site.
Drug Interactions:
- Allopurinol may increase the incidence of skin rashes.
- May reduce the effectiveness of oral contraceptives.
- Increased toxicity risk when combined with methotrexate or anticoagulants.
Nursing Considerations:
- Take oral ampicillin 30 minutes before food.
- Monitor for allergic reactions after administration.
- Avoid mixing aminoglycosides with ampicillin during IV administration.
AMOXICILLIN
Dosage: 250-500 mg every 8 hours.
Pharmacokinetics:
- Well absorbed orally; not affected by food.
- Distributed in lungs, prostate, ears, tonsils, and sputum.
- Partially metabolized in the liver and excreted in urine.
Indications:
- Pneumonia, urinary tract infections, dental abscess, Lyme disease, otitis media, Helicobacter pylori eradication, biliary tract infections, sinusitis, chronic bronchitis.
Contraindications:
- Known hypersensitivity to penicillin, infectious mononucleosis, penicillin-associated jaundice.
Side Effects:
- Nausea, vomiting, diarrhea, skin rash, hepatitis, serum sickness-like syndrome, hemolytic anemia, urticaria.
Drug Interactions:
- May decrease effectiveness of oral contraceptives.
- Allopurinol may increase the incidence of skin rashes.
- Probenecid may increase blood concentration and risk of toxicity.
Nursing Considerations:
- Ensure the client completes the prescribed course of treatment.
CLOXACILLIN
Description: Cloxacillin is resistant to destruction by penicillinase, making it effective against beta-lactamase-producing Staphylococcus aureus.
Pharmacokinetics:
- Poorly absorbed (50%); absorption reduced by food.
- Partially metabolized in the liver and excreted unchanged in urine.
Indications:
- Septicaemia, impetigo, staphylococcal endocarditis, pyomyositis, cellulitis, pneumonia, septic arthritis, osteomyelitis, prophylaxis in bone and joint surgery.
Contraindications:
- Known hypersensitivity.
Side Effects:
- Serum sickness-like reactions, antibiotic-associated colitis, joint pains, hemolytic anemia, candidiasis, diarrhea, skin rashes, nausea, vomiting, urticaria, hepatitis, pain, and inflammation at the injection site.
Drug Interactions:
- Synergistic effect with aminoglycosides; probenecid decreases renal excretion and oral contraceptive effectiveness.
Nursing Considerations:
- Administer on an empty stomach or one hour before meals.
- Complete the prescribed treatment to avoid relapse.
AMOXICILLIN + CLAVULANIC ACID
Mechanism: Clavulanic acid binds to beta-lactamase, protecting amoxicillin from degradation.
Indications:
- Pneumonia, sinusitis, urinary tract infections, wound infections, cellulitis, dental infections, animal bites, otitis media, tonsillitis, urethritis, boils, osteomyelitis, intra-abdominal sepsis, septic abortion, acute exacerbation of chronic bronchitis.
Contraindications:
- Known hypersensitivity to penicillin.
- History of jaundice or hepatic dysfunction associated with penicillin or amoxicillin.
Side Effects:
- Diarrhea, nausea, vomiting, skin rashes, urticaria, gastritis, abdominal discomfort, vaginitis, anorexia, antibiotic-associated colitis.
Drug Interactions:
- Reduces effectiveness of oral contraceptives.
- Allopurinol may increase skin rash incidence.
- Probenecid decreases renal excretion.
Nursing Considerations:
- Take with meals to minimize gastrointestinal disturbance.
- Maintain adequate hydration to prevent crystalluria.
- Store parenteral clavulanic acid immediately after mixing; tablets in airtight containers due to degradation risk.
CEPHALOSPORINS
Description: Cephalosporins are semisynthetic beta-lactam antibiotics that are broad-spectrum and less susceptible to beta-lactamases. They are used when penicillins prove ineffective.
Mechanism of Action: Cephalosporins are bactericidal, inhibiting bacterial cell wall synthesis.
Classification:
- First Generation: Cephalexin, Cefadroxil, Cefazolin (effective against gram-positive bacteria, limited gram-negative activity).
- Second Generation: Cefuroxime, Cefaclor (increased gram-negative activity).
- Third Generation: Ceftriaxone, Ceftazidime (more effective against resistant gram-negative bacteria).
- Fourth Generation: Cefepime (increased activity against gram-negative organisms).
PHARMACOKINETICS OF CEPHALOSPORINS
CEFTRIAXONE
Definition: Ceftriaxone is a broad-spectrum cephalosporin antibiotic, primarily used to treat various bacterial infections. It is effective against a wide range of Gram-positive and Gram-negative bacteria.
Mechanism of Action:
Ceftriaxone works by inhibiting bacterial cell wall synthesis, leading to cell lysis and death. It binds to penicillin-binding proteins (PBPs), which are essential for cell wall integrity.
Available Preparations:
- Injection: Available as a powder for reconstitution in vials (1 g, 2 g).
Dosage:
Adults:
- Typical dose: 1-2 g IV/IM once daily.
- In severe infections, doses may be increased to 4 g daily.
Children:
- For children over 12 years or those weighing more than 50 kg, doses similar to adults may be used.
- For younger children: 50-75 mg/kg/day, given once daily or divided every 12 hours.
Pharmacokinetics:
- Absorption: Administered parenterally (IV or IM); not absorbed well from the gastrointestinal tract.
- Distribution: Widely distributed in body tissues and fluids, including the central nervous system (CNS). It crosses the placenta and is excreted in breast milk.
- Metabolism: Minimal hepatic metabolism.
- Excretion: Primarily excreted unchanged in urine; about 50-60% of a dose is eliminated by the kidneys.
Indications:
Ceftriaxone is used to treat a variety of infections, including:
- Respiratory Tract Infections: Pneumonia, bronchitis, and infections caused by Streptococcus pneumoniae and Haemophilus influenzae.
- Skin and Soft Tissue Infections: Including cellulitis and abscesses.
- Bone and Joint Infections: Such as osteomyelitis and septic arthritis.
- Intra-abdominal Infections: Complicated intra-abdominal infections (often combined with metronidazole).
- Meningitis: Effective against common pathogens causing bacterial meningitis.
- Gonorrhea: Treatment of uncomplicated gonococcal infections.
- Sepsis: Empirical treatment for severe infections and septic shock.
Contraindications:
- Known hypersensitivity to ceftriaxone or other cephalosporins.
- Severe allergic reactions to penicillin (cross-reactivity possible).
- Newborns (particularly those requiring calcium treatment, due to risk of precipitation).
Side Effects:
Common Side Effects:
- Nausea and vomiting
- Diarrhea
- Abdominal pain
- Rash
- Local irritation at injection site
Serious Side Effects:
- Allergic reactions (anaphylaxis)
- Superinfection (overgrowth of non-susceptible organisms)
- Clostridium difficile-associated diarrhea (CDAD)
- Hemolytic anemia
- Liver enzyme elevations
Drug Interactions:
- Probenecid: Can increase ceftriaxone levels by inhibiting renal excretion.
- Calcium: Caution when administered simultaneously, especially in neonates, as it may lead to precipitation in the lungs and kidneys.
- Anticoagulants: May enhance the anticoagulant effect of warfarin; monitoring is advised.
Nursing Considerations:
Administration: Ceftriaxone should be given IV or IM; ensure proper reconstitution if using the powder form.
Monitoring:
- Monitor for signs of allergic reactions, especially after the first dose.
- Assess liver and kidney function, as well as blood counts.
- Watch for gastrointestinal symptoms and signs of superinfection.
Patient Education:
- Advise patients to report any signs of rash, itching, or swelling.
- Instruct on the importance of completing the full course of antibiotics.
- Inform about potential side effects, including diarrhea, and when to seek medical attention.
CARBAPENEMS
Description: Carbapenems are broad-spectrum beta-lactam antibiotics resistant to most beta-lactamases.
Examples:
- Imipenem + Cilastatin
- Meropenem
- Ertapenem
Pharmacokinetics:
- Poor oral absorption; administered IV.
- Widely distributed with high tissue concentrations.
- Eliminated primarily through renal excretion.
Indications:
- Complicated infections, intra-abdominal infections, CNS infections, skin and soft tissue infections, septicemia, and respiratory tract infections.
Contraindications:
- Known hypersensitivity.
Side Effects:
- Nausea, vomiting, diarrhea, hypersensitivity reactions, seizures, rash, headache.
Drug Interactions:
- Probenecid can increase levels of carbapenems; concurrent use with valproic acid may reduce levels.
Nursing Considerations:
- Monitor renal function and signs of hypersensitivity.
- Educate patients about potential side effects.
- Administer as a slow IV infusion.
MACROLIDES
Macrolides are a group of antibiotics derived from Streptomyces species. They exhibit primarily bacteriostatic activity but can be bactericidal against some bacteria at higher concentrations.
Mechanism of Action:
Macrolides inhibit bacterial protein synthesis by binding to the 50S ribosomal subunit. This action disrupts the translation process, ultimately preventing the growth and replication of bacteria.
Examples of Macrolides:
- Erythromycin
- Azithromycin
- Clarithromycin
- Roxithromycin
Erythromycin
Available Preparations:
- Tablet: 250 mg
- Powder for Oral Suspension: 125 mg/5 mL
Dosage:
- Adults: 250-500 mg
- Children: 125-250 mg
Pharmacokinetics:
- Absorption: Adequately absorbed from the gastrointestinal tract; optimal absorption occurs 1-2 hours after meals.
- Distribution: Widely distributed in tissues; crosses the placenta and is secreted in breast milk.
- Metabolism: Primarily metabolized in the liver.
- Excretion: Excreted in bile.
Indications:
- Pneumonia
- Campylobacter enteritis
- Acne vulgaris
- Chancroid
- Prostatitis
- Acute otitis media
- Sinusitis
- Whooping cough
- Lymphogranuloma venereum
- Skin and soft tissue infections
- Non-gonococcal urethritis
- Bronchitis
- Neonatal conjunctivitis
- Pharyngitis and tonsillitis
Contraindications:
- Allergy to macrolides
- Porphyria
- Severe hepatic impairment
Side Effects:
- Nausea
- Abdominal discomfort
- Urticaria
- Reversible hearing loss
- Vomiting
- Diarrhea
- Skin rash
- Pancreatitis
Drug Interactions:
Increases plasma concentrations of carbamazepine.
May inhibit the metabolism of dexamethasone, hydrocortisone, and prednisolone.
Increases the anticoagulant effect of warfarin.
Nursing Considerations for Erythromycin:
Administer on an empty stomach for optimal absorption unless gastrointestinal upset occurs, in which case it can be taken with food.
Inform the patient about potential drug interactions and the necessity to consult a healthcare provider before taking additional medications.
Monitor liver function, and discontinue use if severe hepatic dysfunction occurs.
Azithromycin
Available Preparations:
- Capsules/Tablets: 250 mg, 500 mg
- Powder for Oral Suspension: 200 mg/5 mL
Dosage:
- Adults: 500 mg once daily
- Children: 200 mg-500 mg once daily
Pharmacokinetics:
- Absorption: Rapidly absorbed from the gut; food reduces its absorption.
- Distribution: Widely distributed in body tissues.
- Metabolism: Partially metabolized in the liver.
- Excretion: Excreted in bile, both unchanged and as metabolites.
Indications:
- Pneumonia
- Skin and soft tissue infections
- Typhoid fever
- Pharyngitis/Tonsillitis
- Trachoma
- Pelvic inflammatory disease
- Bronchitis
- Pertussis (whooping cough)
- Sinusitis
- Otitis media
- Traveler’s diarrhea
- Mycobacterium avium complex (MAC) infections
- Non-gonococcal urethritis
indications:
Known hypersensitivity to macrolides
Severe hepatic impairment
Side Effects:
Anorexia
Nausea
Vomiting
Dyspepsia
Constipation
Headache
Dizziness
Taste disturbances
Vertigo
Flatulence
Abdominal discomfort
Convulsions
Somnolence
Skin rash
Drug Interactions:
Concurrent administration of antacids containing aluminum or magnesium salts can reduce the absorption rate but not the extent of absorption.
Avoid concomitant use with lumefantrine and artemether.
Plasma concentrations of azithromycin may be increased by ritonavir.
Azithromycin increases the plasma concentration of digoxin.
Enhances the anticoagulant effect of warfarin.
The effectiveness of oral contraceptives may be reduced by azithromycin.
Nursing Considerations for Azithromycin:
- Shake the suspension well before use.
- Administer on an empty stomach (one hour before or two hours after meals).
- Once-daily dosing is recommended due to its long half-life.
TETRACYCLINES
Tetracyclines are broad-spectrum antibacterial drugs derived from Streptomyces species. They are effective against both gram-positive and gram-negative bacteria and are active against organisms like mycoplasma, chlamydiae, spirochetes, and rickettsiae. However, due to widespread bacterial resistance, they are no longer the first-line treatment for many infections.
Mode of Action:
- Bacteriostatic, inhibiting bacterial protein synthesis by reversibly binding to the 30S subunit of the bacterial ribosome.
Types of Tetracyclines:
- Tetracycline
- Doxycycline
- Minocycline
- Oxytetracycline
Tetracycline
Available Preparations:
- Capsules 250mg
- Eye ointment 1%
- Skin ointment 3%
Pharmacokinetics:
- Well absorbed but reduced by food presence.
- Widely distributed to body tissues and fluids.
- Partially metabolized in the liver.
- Excreted unchanged in the urine.
Dose:
- Adults: 250-500mg
Indications:
- Brucellosis
- Acne vulgaris
- Trachoma
- Lymphogranuloma venereum
- Bronchitis
- Non-gonococcal urethritis
- Malaria
- Gonorrhea
- Shigellosis
- Rosacea
- Cholera
- Pharyngitis
- Sinusitis
- Periodontal disease
Contraindications:
- Children below 12 years
- Pregnant and breastfeeding mothers
- Known hypersensitivity to tetracyclines
Side Effects:
- Anorexia
- Nausea
- Diarrhea
- Sore throat
- Photosensitivity
- Epigastric distress
- Vomiting
- Stomatitis
- Headache
- Hypersensitivity reactions
Doxycycline
Available Preparations:
- Capsules 100mg
- Tablets 100mg
Dose:
- Adults: 100mg twice daily (bd)
Pharmacokinetics:
- Well absorbed orally.
- Widely distributed to body tissues and fluids.
- Excreted in feces.
Indications:
- Acne vulgaris
- Anthrax
- Syphilis
- Exacerbation of chronic bronchitis
- Acute bacterial sinusitis
- Pelvic inflammatory disease (PID)
- Non-gonococcal urethritis
- Malaria treatment and prevention
- Recurrent aphthous ulcer
Contraindications:
- Children under 8 years (causes staining and occasionally dental hypoplasia)
- Pregnant and breastfeeding mothers
- Hypersensitivity to tetracyclines
- Porphyria
Side Effects:
- Nausea
- Vomiting
- Loss of appetite
- Esophageal irritation
- Permanent staining of teeth
- Vaginal candidiasis
- Flushing
- Diarrhea
- Headache
- Tinnitus
- Photosensitivity
Drug Interactions:
- Antacids, iron, calcium, and magnesium preparations impair absorption.
- Doxycycline may increase the anticoagulant effect of oral anticoagulants.
- Decreases therapeutic effect of penicillins.
- May reduce the efficacy of oral contraceptives.
Nursing Considerations:
- Should be taken with plenty of water to reduce esophageal irritation risk.
- Avoid use in children below 12 years.
- Photosensitivity may occur with prolonged sun exposure.
AMINOGLYCOSIDES
Aminoglycosides are antibacterial drugs derived from Actinomycetes species (Streptomyces and Micromonospora). They are poorly absorbed from the gastrointestinal tract, so they are administered via injection for systemic infections or topically for skin, mucous membrane, and ocular infections. Co-administration with cell wall-acting drugs like penicillins enhances their effectiveness.
Mode of Action:
- Bactericidal, inhibiting protein synthesis by irreversibly binding to the 30S ribosomal subunit and causing cell membrane damage.
Types of Aminoglycosides:
- Gentamicin
- Streptomycin
- Tobramycin
- Paromomycin
- Amikacin
- Neomycin
- Kanamycin
Gentamicin
Available Preparations:
- Injection 80mg/2mL
- Ear/Eye drops 0.3%
- Skin ointment 0.1%
Pharmacokinetics:
- Completely absorbed from IM injection sites.
- Distributed to tissues and fluids, including urine (poor CSF penetration).
- Excreted unchanged in urine; accumulates in renal impairment.
Dose:
- Adults: 3-5 mg/kg daily (IM/IV)
- Children (1 month-12 years): 2.5 mg/kg
Indications:
- Urinary tract infections
- Bacterial endocarditis
- Pelvic inflammatory disease
- Skin infections (burns, ulcers)
- Surgical prophylaxis
- Biliary tract infections
- Otitis externa
- Brucellosis
- Pneumonia
- Septicemia
- Neonatal sepsis
Contraindications:
- Hypersensitivity to aminoglycosides
- Myasthenia gravis
Side Effects:
- Nephrotoxicity
- Ototoxicity
- Headache
- Rash
- Nausea
Diarrhea
Blood disorders
Drug Interactions:
- Increases nephrotoxicity risk with amphotericin B.
- Increases ototoxicity risk with frusemide.
- Vancomycin increases nephrotoxicity and ototoxicity risks.
- Suxamethonium increases muscle relaxation effects.
Nursing Considerations:
- Administer penicillins or cephalosporins at least one hour before or after gentamicin to avoid incompatibility.
- Adjust dose in renal impairment.
- Use cautiously in elderly patients due to the risk of renal and auditory impairment.
SULPHONAMIDES & TRIMETHOPRIM
Sulphonamides are a class of antibacterial agents structurally related to para-aminobenzoic acid (PABA). Their therapeutic importance has decreased due to widespread resistance. Trimethoprim is often combined with sulphonamides, specifically sulfamethoxazole, to form co-trimoxazole, increasing their effectiveness.
Mode of Action:
- Sulphonamides are bacteriostatic, inhibiting bacterial folic acid synthesis.
- Trimethoprim blocks bacterial dihydrofolate reductase, further inhibiting folate synthesis.
Types of Sulphonamides:
- Cotrimoxazole (Trimethoprim + Sulfamethoxazole)
- Sulphadiazine
- Sulfasalazine
- Sulphamethoxazole
- Silver sulphadiazine
- Sulphadoxine
Classification of Sulphonamides:
- Rapidly absorbed and excreted: Sulphamethoxazole, Sulphadiazine
- Poorly absorbed, active in bowel lumen: Sulfasalazine
- Topical use: Silver sulphadiazine
- Long-acting: Sulphadoxine
Cotrimoxazole (Trimethoprim + Sulfamethoxazole)
Available Preparations:
- Tablets: 480mg, 960mg
- Oral suspension: 240mg/5mL
- Injection for infusion: 960mg/3mL
Dose:
- Adults (oral): 960mg per dose
- Children: 24mg/kg per dose
Pharmacokinetics:
- Well absorbed after oral administration.
- Widely distributed to tissues and fluids.
- Excreted in urine.
Indications:
- Urinary tract infections
- Granuloma inguinale
- Toxoplasmosis
- Brucellosis
- Shigellosis
- Pneumocystis carinii pneumonia (PCP)
- Pneumonia
- Bronchitis
- Otitis media
- Traveler’s diarrhea
Contraindications:
- Hypersensitivity to sulphonamides or trimethoprim
- Severe renal or hepatic failure
- Neonates
Side Effects:
- Nausea
- Headache
- Skin rash
- Urticaria
- Anorexia
- Photosensitivity reactions
- Diarrhea
- Itching
- Renal failure
- Hyperkalemia
- Stomatitis
Drug Interactions:
- Co-trimoxazole may increase digoxin levels.
- Oral contraceptive efficacy may be reduced.
- Co-trimoxazole increases the anticoagulant effect of warfarin.
- May enhance the blood glucose-lowering effects of oral antidiabetics.
Nursing Considerations:
- Ensure patients on co-trimoxazole take plenty of fluids to reduce crystalluria and potential kidney damage.
- Monitor patients closely for life-threatening reactions and discontinue if any signs appear.
QUINOLONES
Quinolones are a class of synthetic antibacterial agents that inhibit bacterial DNA synthesis by targeting DNA gyrase and topoisomerase IV. They are bactericidal and effective against a broad range of gram-negative and some gram-positive bacteria. Quinolones are classified into generations based on their spectrum of activity.
Classification of Quinolones:
- First-generation: Nalidixic acid
- Second-generation: Ciprofloxacin, Norfloxacin, Ofloxacin, Pefloxacin, Lomefloxacin
- Third-generation: Levofloxacin, Sparfloxacin, Gatifloxacin, Moxifloxacin
Nalidixic Acid
Available Preparations:
- Tablets: 500mg
Pharmacokinetics:
- Well absorbed from the gastrointestinal tract.
- Concentrates in renal tissues and seminal fluid.
- Metabolized in the liver to a more active form.
- Excreted in urine.
Indications:
- Urinary tract infections
- Shigellosis
Contraindications:
- Hypersensitivity
- History of epilepsy
- CNS lesions
Dose:
- Adults: 500mg-1g every 6 hours
- Children (>3 months): 15-50mg/kg every 6 hours
Side Effects:
- Nausea
- Dizziness
- Confusion
- Vomiting
- Vertigo
- Weakness
- Skin rash
- Urticaria
- Headache
- Cranial nerve palsy
- Diarrhea
- Visual disturbances
- Abdominal pain
- Convulsions
Drug Interactions:
- Probenecid prolongs the half-life of nalidixic acid.
- Increased risk of bleeding with oral anticoagulants.
Nursing Considerations:
- Advise patients to take nalidixic acid on an empty stomach, preferably one hour before meals.
Ciprofloxacin
Available Preparations:
- Tablets: 500mg, 1g
- Injection: 200/100mL
- Eye drops: 0.3% w/v
Pharmacokinetics:
- Rapidly and well absorbed when taken orally, with 70-80% bioavailability.
- Widely distributed throughout the body, with good tissue and bone penetration.
- Metabolized in the liver.
- Excreted in urine and feces.
Indications:
- Urinary tract infections
- Surgical prophylaxis
- Chronic prostatitis
- Traveler’s diarrhea
- Shigellosis
- Peritonitis
- Gonorrhea
- Respiratory tract infections
- Prophylaxis of meningococcal meningitis
- Septicemia
- Typhoid
- Chancroid
- Cholera
- Otitis externa
- Bone and joint infections
- Anthrax
Contraindications:
- Breastfeeding
- Pregnancy
- Allergy to ciprofloxacin
- Children below 18 years
Dose:
- Oral (adults): 250-750mg twice daily
Side Effects:
- Headache
- Restlessness
- Palpitations
- Diarrhea
- Drowsiness
- Depression
- Nausea and vomiting
- Urticaria
- Anorexia
- Dizziness
- Lightheadedness
- Skin rash
- Convulsions
- Dyspepsia
- Tremors
- Abdominal discomfort
- Insomnia
Drug Interactions:
- Antacids containing aluminum and magnesium interfere with absorption.
- Concomitant use with probenecid increases ciprofloxacin plasma levels.
- Ciprofloxacin increases phenytoin, theophylline, and anticoagulant blood levels.
- Efficacy is reduced by iron salts and sucralfate.
- May increase the effects of oral anticoagulants.
Nursing Considerations:
- Ciprofloxacin should be taken one hour before or two hours after meals for optimal absorption.
- Advise patients to drink plenty of fluids while on ciprofloxacin.
- Patients should avoid taking dairy products, antacids, iron, zinc, or calcium supplements with ciprofloxacin.
- Ciprofloxacin may increase the effects of caffeine, so advise patients to reduce caffeine intake.
- It may worsen seizures in epileptic patients.
NITROIMIDAZOLES
Nitroimidazoles are a class of antimicrobial agents that are primarily effective against anaerobic bacteria and protozoa. They work by disrupting DNA synthesis in these microorganisms.
Mechanism of Action: Nitroimidazoles, including metronidazole, are prodrugs that require reduction by anaerobic bacteria or protozoa to become active. The reduced form interacts with DNA, causing strand breakage and inhibiting nucleic acid synthesis, ultimately leading to cell death.
METRONIDAZOLE
Description: Metronidazole is a synthetic nitroimidazole antibiotic with antiprotozoal and antibacterial properties, particularly effective against anaerobic bacteria and certain protozoa such as Trichomonas vaginalis, Entamoeba histolytica, and Giardia lamblia.
Pharmacokinetics:
- Absorption: Rapidly and well absorbed from the gastrointestinal tract; food does not significantly affect absorption.
- Distribution: Widely distributed in body tissues and fluids, including the CNS and saliva.
- Metabolism: Primarily metabolized in the liver.
- Excretion: Excreted mainly through urine as metabolites.
Dosage:
- Adult Dose: Varies based on infection; typically, 500 mg orally 2-3 times daily for infections.
Indications
- Bacterial Infections: Anaerobic infections, including intra-abdominal infections, pelvic inflammatory disease, and skin and soft tissue infections.
- Protozoal Infections:
- Trichomoniasis
- Giardiasis
- Amoebic dysentery
- Clostridium difficile Infection: Used in treatment of mild to moderate cases.
- Surgical Prophylaxis: Particularly in colorectal surgery.
Other Uses: Treatment of H. pylori eradication in peptic ulcer disease, rosacea, and bacterial vaginosis.
Contraindications
- Known Hypersensitivity: Avoid in patients with a history of hypersensitivity to metronidazole or other nitroimidazoles.
- First Trimester of Pregnancy: Use with caution; avoid unless absolutely necessary.
Side Effects
- Gastrointestinal: Nausea, vomiting, diarrhea, abdominal pain, metallic taste.
- Neurological: Headaches, dizziness, peripheral neuropathy (with long-term use).
- Dermatological: Rash, urticaria, Stevens-Johnson syndrome (rare).
- Other: Darkening of urine, seizures (rare, with overdose).
Drug Interactions
- Alcohol: Concurrent use can lead to a disulfiram-like reaction (flushing, nausea, vomiting).
- Anticoagulants: May enhance the effects of warfarin and other anticoagulants, increasing bleeding risk.
- Lithium: Metronidazole may increase lithium levels, leading to toxicity.
- CYP450 Inhibitors: May interact with drugs metabolized by CYP enzymes, potentially increasing their effects.
Nursing Considerations
- Administering Medication: Metronidazole can be given orally or intravenously; for intravenous administration, infuse slowly to prevent infusion reactions.
- Patient Education:
- Instruct patients to avoid alcohol during treatment and for at least 48 hours after discontinuation.
- Advise patients about potential side effects, including gastrointestinal disturbances and metallic taste.
- Monitoring:
- Monitor liver function tests, especially in patients with hepatic impairment.
- Assess for signs of peripheral neuropathy, particularly with prolonged use.
- Ensure patients complete the full course of therapy to prevent resistance.