PHARMACOLOGY - ANTIBIOTICS

Pharmacology of the Antibiotics Nurse Licensure Examination Review

The anti-infectives
ANTI-INFECTIVES
Anti-infective agents are drugs that are designed to act selectively on foreign organisms that have invaded and infected the body
Anti-infectives- range from antibiotics, antifungals, antiprotozoals, antihelmintics, antivirals and antimycobacterial.

General Mechanisms of Action of anti-infective
Some interfere with the biosynthesis of bacterial cell WALL
Some inhibit protein synthesis
Some change the cell membrane permeability
Some inhibit DNA synthesis

Spectrum of Activity of Anti-infectives
Narrow spectrum anti-infectives affect only a few bacterial types. The early penicillin drugs are examples.
Broad-spectrum anti-infectives affect many bacteria. Meropenem is an example. Because narrow spectrum antibiotics are selective, they are more active against those single organisms than the broad spectrum antibiotics.

Spectrum of Activity of Anti-infectives
Anti-infectives that interfere with the ability of the cell to reproduce/replicate without killing them are called BACTERIOSTATIC drugs. Tetracycline is an example.
Antibiotics that can aggressively cause bacterial death are called BACTERICIDAL. These properties (-cidal and –static) can also depend on the antibiotic concentration in the blood.

Common Adverse Reactions to Anti-infective Therapy
The most common adverse effects are due to the direct action of the drugs in the following organ system- Neuro, nephro and GI system
1. Nephrotoxicity
Antibiotics that are metabolized and excreted in the kidney most frequently cause kidney damage..

2. Gastro-intestinal toxicity
Direct toxic effect to the cells of the GI tract can cause nausea, vomiting, stomach pain and diarrhea. Some drugs are toxic to liver cells and can cause hepatitis or liver failure.

3. CNS toxicity
When drugs can pass through the brain barrier and accumulate in the nervous tissues, they can interfere with neuronal function.

4. Hypersensitivity
Most protein antibiotics can induce the body’s immune system to produce allergic responses. Drugs are considered foreign substances and when taken by the individual, it encounters the body’s immune cells.

5. Superinfections
Opportunistic infections that develop during the course of antibiotic therapy are called SUPERINFECTIONS.

The PENICILLINS
Narrow spectrum penicillins
Penicillin G
Penicillin V
Broad Spectrum Penicillins (aminopenicillin)
Amoxicillin
Ampicillin
Bacampicillin
Penicillinase-resistant Penicillin (anti-staphyloccocal penicillins)
Cloxacillin
Nafcillin
Methicillin
Dicloxacillin
Oxacillin
Extended-Spectrum penicillins (Anti-pseudomonal penicillins)
Carbenicillin
Mezlocillin
Piperacillin
Ticacillin
Beta-lactamase inhibitors
Clavulanic acid
Sulbactam
Tazobactam

Penicillin
The structure of Penicillin
Penicillin is a beta-lactam drug, with a beta-lactam ring. The group of penicillins is called beta lactam antibiotics.

Penicillin
Pharmacodynamcs: The action of Penicillins
The penicillin and penicillinase-resistant penicillins produce BACTERICIDAL effects by interfering with the ability of susceptible bacteria from biosynthesizing the framework of the cell wall.
The bacterium will have weakened cell wall, will swell and then burst from the osmotic pressure within the cell.

Amoxicillin is well absorbed in the GIT

Therapeutic Indications of penicillin
The penicillins are indicated for the treatment of streptococcal infections.

Adverse Effects of Penicillins
GI system effects- the major adverse effects of penicillin therapy involve the GIT. Nausea, vomiting, diarrhea, abdominal pain, glossitis, stomatitis, gastritis, sore mouth and furry tongue.
The reason for some of these effects (superinfection) is associated with the loss of bacterial flora.
Hypersensitivity reactions- rashes, pruritus, fever. These indicate mild allergic reaction. Wheezing and diarrhea may also occur. Anaphylaxis can also happen leading to shock or death. It occurs in 5-10% of those receiving penicillins.
Pain and inflammation on injection sites

IMPLEMENTATION
Obtain culture and sensitivity testing results to check if penicillin is the drug of choice
Monitor the renal status and function regularly
Administer the correct dosage and stress the importance of completing the full course and duration of therapy even though the patient experiences relief earlier in the treatment

Monitor the site of injection and the signs and symptoms related to the drug administration
Provide small frequent meals, frequent mouth care, ice chips or sugarless candy to suck if stomatitis and sore mouth occurs.
Provide patient teaching. Tell the patient to drink a lot of fluids and eat nutritious foods. Advise to report difficulty of breathing, severe diarrhea, dizziness, weakness and vaginal itching.

EVALUATION
Monitor patient response to therapy
Monitor for adverse effects and evaluate the effectiveness of health teaching
Monitor the effectiveness of comfort and safety measures

THE CEPHALOSPORINS
First Generation cephalosporins- are largely effective against the same gram-positive organisms affected by penicillin.
Second generation cephalosporins- are effective against those strains as well as Haemophilus influenza, Entreobacter aerogenes and Nesseria sp. These drugs are less effective against gram positive bacteria
Third Generation cephlosporins- are relatively weak against gram-positive bacteria but more potent against gram-negative bacteria, to include Serratia marcescens.
Fourth generation cephalosporins- are developed to fight against the resistant gram-negative bacteria. The first drug is cefepime.
First generation cephalosporins
cefadroxil
Cefazolin
Cephalexin
Cephalotin
Cephapirin
Cephadrine
Second Generation cephalosporins
Cefaclor
Cefamandole
Cefonizind
Cefotetan
Cefoxitin
Cefmetazole
Cefprozil
Cefuroxime
Third Generation Cephaosporins
Cefnidir
Cefixime
Cefoperazone
Cefotaxime
Cefpodoxime
Ceftazidime
Ceftibuten
Moxalactam
Fourth Generation Cephalosporin
Cefepime

Pharmacodynamics; The mechanism of action of cephalosporins
The cephalosporins are primarily BACTERICIDAL. They interfere with the cell-wall building ability of bacteria when they divide. They prevent the bacteria from biosynthesizing the framework of their cell wall. The weakened cell wall will swell and burst causing cell death.
Pharmacokinetics
Only a few cephalosporins are administered orally, most are administered parenterally. Their half-lives are short and they are excreted mainly in the urine.
Contraindications and Precautions
The drugs are contraindicated in patients with known allergies to cephalosporins and penicillins.
Adverse Effects
GI system- Nausea, vomiting, diarrhea, anorexia, abdominal pain and flatulence are common effects.
CNS – headache, dizziness, lethargy and paresthesias have been reported.
Renal system- nephrotoxicity in individuals with pre-existing renal disease
Drug-Drug interactions
Aminoglycosides- if given with cephalosporins may increase the risk of kidney toxicity
Anti-coagulants- may experience increased bleeding tendencies
ALCOHOL- many patients experience a disulfiram-like reactions when taken with some specific cephlosporins ( cefamandole, cefoperazone or moxalactam). The patient may experience flushing, headache, nausea, vomiting and muscular cramps. This may occur even up to 72 hours of cephalosporin discontinuance.
The Nursing Process and Cephalosporins
ASSESSMENT
Patient History- The nsure must assess for cephalosporin and penicillin allergies. Pregnancy, lactation and kidney status must also be ascertained
Physical Examination- baseline data for evaluation. Renal function should be checked by obtaining BUN and Creatinine levels, urine output monitoring and temperature monitoring.
DIAGNOSIS
Pain related to GIT and CNS effects
High risk for infection
Fluid volume deficit
Knowledge deficit
Non-compliance with medication
IMPLEMENTATION
Check the culture and sensitivity results to determine if cephalosporin is the drug of choice
Monitor renal function test prior to and periodically during therapy
Ensure that the patient receives the full course of cephalosporins as prescribed for the duration specified. Advise the patient to consume all the drugs even though signs/symptoms may resolve earlier in the course.
Provide small frequent meals as tolerated, mouth care, ice chips if stomatitis occurs.
Provide safety measures including safety side-rails, adequate lighting and assistance with ambulation.
Provide heath teaching and advise the patient to take safety precaution in changing positions carefully, avoid driving and hazardous tasks, drink fluids liberally, report severe reactions to the drug and AVOID alcoholic beverages for 72 hours after completing the drug.
Take medication with food if gastric irritation occurs.
EVALUATION
Monitor patient response to the drug regimen
Monitor for adverse effects and evaluate the effectiveness of comfort and safety measures

The Aminoglycosides
The following are the aminoglycosides
1.Gentamycin
2.Tobramycin
3.Amikacin
4.Netilmicin
5.Kanamycin
Pharmacodyanmics:
These are BACTERICIDAL. They inhibit protein synthesis in susceptible strains of gram-negative bacteria, leading to loss of functional integrity of the bacterial cell membrane, which causes cell death.
Therapeutic Use of the Aminoglycosides
These drugs are used to treat serious infections caused by gram-NEGATIVE bacteria.
Contraindications and Precautions with the use of Aminoglycosides
These drugs are contraindicated in known allergies to aminoglycosides, in patients with renal failure, hepatic disease, pre-existing hearing loss, myasthenia gravis, Parkinson’s, pregnancy and lactation.
Adverse Effects of Aminoglycosides
CNS- irreversible deafness, vestibular paralysis, confusion, depression, disorietnation, numbness, tingling and weakness related to drug effects.
Kidney- renal toxicity, which may progress to renal failure caused by the direct toxicity of the aminoglycosides.
Hema- bone marrow depression resulting from direct drug effect may lead to immune suppression and superinfection.
GI system- nausea, vomiting, diarrhea, weight loss, stomatiits and hepatic toxicity. The effects are due to the direct GI irritation, loss of bacterial flora and toxicity to mucucs membrane and liver as the drugs are metabolized.
Skin effects- photosensitivity, purpura, rash, urticaria and exfoliative dermatitis
Cardiac- palpitaions, hypotension or hypertension
Drug to drug interactions
Diuretics- increased incidence of ototoxicity, nephrotoxicity and neurotoxicity.
Anesthetics and Neuromusular blockers- increased neuromuscular blockage and paralysis may be possible
Penicillin- synergistic action
The Nursing Process and Aminoglycosides
ASSESSMENT
Patient History- the nurse assesses the allergy to aminoglycosides, history of renal and hepatic disease, parkinsonism, myasthenia gravis, existing hearing loss, active herpes infecion, current pregnancy and lactation.
Physical examination- baseline data should be obtained. Auditory and CNS assessement must be done prior to thrapy. Culturea nd sensitivity specimen must be sent to laboratory. Renal and hepatic function tests should be checked.
DIAGNOSIS
Pain related to GU, CNS effects
Sensory-Perceptual alteration
Potential for infection
Fluid volume excess related to nephrotoxicity
Knowledge deficit
IMPLEMENTATION
Check the culture and sensitivity results to determine if aminoglycosides are the drug of choice.
Monitor the course of therapy. Ensure that the patient receives the correct dose and duration of treatment.
Monitor the patient regularly for signs of nephrotoxicity, neurotoxicity, ototoxicity and bone marrow depression to effectively arrange for discontinuation of drug or decreased dosage as appropriate
Provide safety measures to protect the patient if CNS effects occur.
Provide small, frequent meals as tolerated, frequent mouth care and ice chips or sugarless and to provide relief and maintain nutrition
Ensure that patient is hydrated at all times during the drug therapy to minimize renal toxicity
Provide teaching to the patient to take safety precaution such as changing position slowly and avoiding driving/hazardous tasks, drink liberal amounts of fluids, avoid exposure to other infections, and to report severe reactions.
EVALUATION
Monitor patient response to the drug, adverse effects and effectiveness of comfort measures
Evaluate the effectiveness of teaching and compliance to regimen.

The Macrolides
The macrolides are
Azithromycin
Clarithromycin
Dirithromycin
Erythromycin
Pharmacodynamics: Mechanism of Action of the Macrolides
The macrolides are primarily BACTERICIDAL and sometimes bacteriostatic. They exert their effect by binding to the bacterial cell ribosomes and changing or altering protein production/function. This will lead to impaired cell metabolism and division.
Pharmacokinetics
Erythromycin is destroyed by the gastric juice, which is why slats are added to stabilize the drug. Food does not interfere with the absorption of the macrolides.
Therapeutic Use of Macrolides
These are indicated for the treatment of the following conditions: Steptococcal infection, Mycoplasma infection, Listeria infection and group A beta hemolytic strep infection.
Contraindications and Precautions in the Use of Macrolides
These agents are contraindicated in the presence of known allergy to any macrolide, because cross-sensitivity occurs. Caution should be used in patients with hepatic dysfunction that could alter the metabolism of the drug; in lactating women because of drug excretion in breast milk and in pregnant women because potential adverse effects on the developing fetus.
Adverse Effects of Macrolides
GI system- abdominal cramping, anorexia, diarrhea, vomiting and pseudomembranous colitis. HEPATOTOXICITY can occur if the drug is taken in high doses with other hepatotoxic drugs.
CNS- confusion, abnormal thinking and uncontrollable emotions.
Hypersensitivity reactions
Drug-Drug Interactions
Digoxin- increased level of dioxin can occur
Anticoagulants, theophyllines and corticosteroids- increased effects of these drugs due to impaired hepatic metabolism
Astemizole- when used with macrolides, will cause fatal cardiac arrhythmias
Clindamycin or lincomycin – should not be given with erythromycin because they compete for receptor sites.
The Nursing Process and Macrolides
ASSESSMENT
Patient History- the nurse should obtain history of allergy, current pregnancy or lactation before administering the drug
Physical Examination- Assess baseline data and perform C/S before instituting therapy. The nurse then obtains information about the status of the liver and kidney, skin and GI system.
DIAGNOSIS
Pain related to GI, CNS effects
Potential for infection related to super infections
Knowledge deficit regarding drug therapy
IMPLEMENTATION
Check culture and sensitivity results to ensure that macrolides are the drug of choice
Monitor hepatic function test prior to therapy
Ensure that patients receive the full course of therapy
Monitor sings and symptoms of adverse reactions
Provide small, frequent meals as tolerated, provide mouth care and ice chips
Provide safety measures to protect patient if CNS effects occur
Provide health teaching and emphasize that the patient should take safety precautions including changing position slowly, drinking liberal amounts of fluids, and reporting severe reactions.
EVALUATION
Monitor patient response to the drug and adverse effects
Evaluate the effectiveness of comfort and safety measures and the effectiveness of health teaching

The Lincosamides
These agents are similar to the Macrolides but are more toxic. They are bactericidal and bacteriostatic depending on the dose.
The following are the Lincosamides:
Clindamycin
lincomycin
Pharmacodynamics: The Mechanism of Action of Lincosamides
These agents penetrate the cell membrane and bind to the ribosome in the bacterial cytoplasm to prevent the protein production
Side effects and Adverse Reactions
GIT- GI irritation, nausea, vomiting and stomatitis
Allergic reactions
Drug Interactions
Lincomycin and clindamycin are incompatible with aminophyline, phenytoin, barbiturates and ampicillin.

The Tetracyclines
These agents were first isolated from Streptomyces aureofaciens
The following are the tetracyclines
Short-acting tetracyclines
tetracycline
oxytetracycline
Intermediate acting tetracyclines
demeclocycline
methacycline
Long acting tetracyclines
doxycycline
minocycline
Pharmacodynamics: The Mechanism of Action of Tetracyclines
The tetracyclines inhibit protein synthesis in susceptible bacteria leading to the inability of the bacteria to multiply.
Therapeutic indications of the Tetracycline
Tetracyclines are effective against a wide range of bacteria. They are primarily BACTERIOSTATIC.
Contraindications and Precautions in the use of Tetracyclines
These agents are contraindicated in the presence of known allergy to tetrayclines and the tartrazine dye. It is not recommended for use in pregnancy and lactation because the drug can affect the bones and teeth, causing permanent discoloration and sometimes arrest of growth. Tetracyclines are also avoided in children less than 8 (eight) years of age because of the potential damage to the bones and permanent discoloration of the teeth.
Adverse Effects of the Tetracycline
GI system- nausea, vomiting, diarrhea, abdominal pain, glossitis and dysphagia. Fatal hepatotoxicity related to tetracycline’s irritating effect on the liver cells has been reported.
Musculoskletal- Tetracyclines have an affinity for teeth and bones; they accumulate there, leading to weakening of the bone/teeth and permanent staining and pitting.
Skin- photosensitivity and rash are expected.
Less frequent- bone marrow depression, hypersensitivity, super infections, pain and hypertension
Drug-Drug Interactions
Penicillin- if taken with tetracyclines, will decrease the effectiveness of penicillin.
Oral contraceptives- if taken with tetracycline, will have decreased effectiveness. Nurse must advise alternative methods of contraception
Digoxin- digoxin toxicity rises when tetracyclines are used together
Drug-Food Interaction
Dairy products- can complex with tetracycline and render unabsorbable. Tetracyclines should then be given on an EMPTY stomach 1 hour before meals or 2-3 hours after any meal or other medications.
The Nursing Process and Tetracyclines
ASSESSMENT
Patient History- The nurse screens the patient for allergy to tetracyclines and tartrazine. She should elicit history of renal and liver diseases, pregnancy, lactation, and AGE. Tetracyclines have adverse effects on the bones and teeth.
Physical Examination- this should be performed to establish baseline data for monitoring. Culture and sensitivity tests should be done and evaluation of kidney and liver status should be done.
DIAGNOSIS
Diarrhea
Alteration in Nutrition: LTBR related to GI effects
Alteration in skin integrity related to rash and photosensitivity
IMPLEMENTATION
Check the culture and sensitivity results to ensure that tetracyclines are the drug of choice
Monitor renal and liver status/function tests periodically
Emphasize the need to complete the recommended duration of therapy
Provide small frequent meals if tolerated only
Protect the patient from exposure to the sun with adequate clothing and sunscreen
Instruct the patient to take the meds without food, with full glass of water, adequate fluid intake, avoidance of exposure to other infections and to report severe drug reactions
Provide information of alternative contraceptive methods during the course of therapy
EVALUATION
Monitor response to tetracycline and adverse effects
Evaluate the effectiveness of teaching an comfort

The Fluoroquinolones
The fluoroquinolones are broad-spectrum antibiotics. They are usually manufactured synthetically and are associated with mild adverse reactions.
The examples are:
1. Nalidixic acid
2. ciprofloxacin
3. oxacillin
4. norfloxacin
5.Levfofloxacin
6.Sparfloxacin
Pharmacodynamics: Mechanism of action of the Fluoroquinolones
These agents enter the bacterial cell by diffusion through cell channel. Once inside they interfere with the action of DNA enzymes (DNA gyrase) necessary for the growth and reproduction of the bacteria. This will lead to cell death.
Therapeutic Use of the Fluoroquinolones
]These agents are indicated for the treatment of infections caused by susceptible strains of gram-negative bacteria including E. coli., Proteus, pseudomonas, Strep and Staph spp.
Contraindications and Precautions
Known drug allergy to these agents contraindicate their use. Pregnancy and lactation are also contraindications. These agents are found to cause significant damage to the cartilages such that they are given cautiously to growing children and adolescents less than 18 years of age.
Adverse Effects of the Fluoroquinolones
CNS- dizziness, insomnia, headache, and depression related to possible effects on the CNS membrane.
GI system- nausea, vomiting, diarrhea and dry mouth related to the direct effect on the GIT
Hema- bone marrow depression related to the direct effect of the drug on the cells of the bone marrow that rapidly turn over.
Other effects- skin reactions, rash, fever and photosensitivity
Drug-Drug Interaction
Iron salts, Sucralfate, mineral supplements and antacids- all of these will decrease the effectiveness of the fluoroquinolones
Quinidine, Procainamide, terfenadine, henothiazines- can prolong the QT interval and when used with the fluoroquinolones

The Sulfonamides
These are called sulfa drugs that inhibit folic acid synthesis. Folic acid is necessary for the synthesis of purine and pyrimidine precursprs of DNA and RNA. Humans cannot produce folic acid and must obtin it form the diet. While bacteria need to manufacture their own folic acid inside their cell structure.
The following are the sulfonamides:
1.Sulfazalazine
2.Sulfamethoxazole
3. Sulfadiazine
4.Sulfixoxazole
Pharmacodynamics: The Mechanism of Action of Sulfonamides
The sulfa drugs competitively block the para-amino benzoic acid to prevent the synthesis of folic acid in susceptible bacteria that synthesize their own folates for the production of RNA and DNA.
Therapeutic indications
The spectrum of activity includes the following bacteria- Chlamydia, Nocardia, Haemophilus, E, coli and Proteus. Sulfa drugs are used to treat trachoma and brain abscess.
Contraindications and precautions
These agents are contraindicated to patients with known allergy to sulfa drugs, sulfonylureas and thiazide diuretics because they share similar structures. It is not recommended for use in pregnancy because it can cross the placenta and cause birth defects and kernicterus. Lactating women who take these drugs will excrete them in the breast milk potentially causing kernicterus, diarrhea and rash in the newborn.
Adverse Effects of the Sulfonamides
GI system- nausea, vomiting, diarrhea, abdominal pain, anorexia, stomatitis and hepatic injury, which are all related to the direct irritation of the GIT and death of normal flora.
Renal system- crystalluria, hematuria and proteinuria which can progress to a nephrotic syndrome.
CNS- headache, dizziness, vertigo, ataxia, convulsions and depression related to drug effects on the nerves
Hema- bone marrow depression related to drug effects on the cells of the bone marrow that turn over rapidly.
Dermatologic effects- photosensitivity and rash and hypersensitivity
Drug-Drug Interaction
Tobultamide, tolazamide, glyburide, glipizide, acetohexamide or chlorpropamide (all are oral Anti-diabetic agents) can increase the risk of hypoglycemia if taken with the sulfa drugs
The Nursing Process and the Sulfonamides
ASSESSMENT
Patient History- The nurse screens for known allergy to sulfonamides, sulfonylureas and thiazide diuretics because of cross sensitivity. Elicit history of renal disease and current pregnancy/lactation
Physical Examination- PE should be performed to establish baseline data for assessing the drug effectiveness. Culture and sensitivity should be performed before instituting therapy. The nurse should also monitor the renal status. CBC should be performed to establish a baseline data to monitor for adverse effects.
DIAGNOSIS
Pain related to GI, CNS and skin effects of the drug
Sensory-Perceptual alteration related to CNS effects
Alteration in nutrition related to multiple GI effects
IMPLEMENTATION
The nurse checks the culture and sensitivity results to ensure that sulfa drugs are the drug of choice
Monitor renal functions test periodically. Discontinue drug if hypersensitivity reaction occurs.
Administer the drug on an EMPTY stomach 1 hour before or 2 hours after meals with full glass of water to ensure adequate drug absorption
Provide mouth care if with stomatitis or mouth problems occur
Monitor CBC and urinalysis periodically.
Implement health teaching. Emphasize that the patient should avoid operating dangerous machinery, drinking liberal amount of fluids, maintain nutrition and to report severe drug reactions.
EVALUATION
Monitor patient response to the drug. Monitor for adverse effects
Evaluate effectiveness of the teaching plan and monitor the effectiveness of safety and comfort measures

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PHARMACOLOGY - ANTIBIOTICS

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PHARMACOLOGY - ANTIBIOTICS — Presentation Transcript