• Antibiotics
• Classification
• Antibiotics selection
• Problems arise with use of Antibiotics
• Why Combination of Antibiotics
• Top 10 Antibiotics
You will know here something interesting about Antibiotics in this article.
Hii dear visitors 😊
Your welcome, you are learning Pharmacology at onlycology.
Hello dear visitors
😊 I hope you've got help, if you have any suggestion or any question regarding this article"Antibiotics,, please comment i will be very happy.
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Also read : Congestive heart failure
ACE inhibitors
Antihypertensive drugs and classification
Classification
,
Pharmacology
• Classification
• Antibiotics selection
• Problems arise with use of Antibiotics
• Why Combination of Antibiotics
• Top 10 Antibiotics
You will know here something interesting about Antibiotics in this article.
Hii dear visitors 😊
Your welcome, you are learning Pharmacology at onlycology.
ANTIBIOTICS
Antibiotics are chemical substances of natural / semisynthetic / synthetic origin, capable of being selectively toxic to pathogen and safe to the parasite, in relatively lower concentrations either by destroying or affecting it's growth/ multiplication.
CLASSIFICATION
Can be classified based on :
A. Chemical structure
1. Sulfonamides and related drugs : Sulfadiazine, Paraaminosalicyclic acid.
2. Diaminopyrimidine : Trimethoprim, pyrimethamine.
3. Quinolones : Norfloxacin, Ciprofloxacin.
4. beta-lactum antibiotics : Penicillin, Cephalosporin, Monobactums, Carbapenems.
5. Tetracyclines : Doxycycline, Oxytetracycline.
6. Nitribenzene derivative :Chloramphenicol.
7. Aminoglycosides : Streptomycin, Gentamycin, Neomycin.
8. Macrolide antibiotics : Erythromycin, Azithromycin.
9. Nitroimidazoles : Metronidazole.
10. Azole derivative : Miconazole, Clotrimazole, Ketoconazole.
11. Nicotinic acid :Pyrazinamide, Ethionamide.
12. Others : Rifampin, Clindamycin, Cycloserine, Viomycin, Thiacetazone.
B. Mechanism of action
1. Inhibit cell wall synthesis : Penicillin, Cephalosporin, Cycloserine, Vanomysin.
2. Cause leakage from cell membrane :Polymixin, Colistin, Amphitericin B, Nystatin, Hamycin.
3. Inhibit protein synthesis : Tetracyclines, Chloramphenicol, Erythromycin, Clindamycin.
4. Cause misreading of m-RNA code and affect permeability : Streptomycin, Gentamycin.
5. Inhibit DNA gyrase : Ciprofloxacin.
6. Interfere with DNA function : Rifampin, Metronidazole.
7. Interfere with DNA synthesis : Idoxuridine, Zidovudine.
8. Interfere with intermediary metabolism : Sulfonamides, Sulfones, Trimethoprim, Pyrimethamine, Ethambutol.
C. Spectrum of activity
1. Narrow spectrum : Penicillin G, Streptomycin, Erythromycin.
2. Broad spectrum : Tetracyclines, Chloramphenicol.
D. Type of action
1. Primarily bacteriostatic : Sulfonamides, Tetracyclines, Erythromycin, Chloramphenicol, Ethambutol.
2. Primarily bactericidal : Penicillin, aminoglycosides, Cephalosporin, vanomycin, Rifampin, Ciprofloxacin, Cotrimoxazole.
E. Antibiotics obtained from
1. Fungi : Penicillin, Cephalosporin, Griseofulvin.
2. Bacteria : Polymyxin B, Colistin, Bacitracin, Tyrothricin, Aztreonam.
3. Actinomycetes : Aminoglycosides, Tetracyclines, Chloramphenicol, Macrolides, Polyenes.
Read important classifications :
Classification of drug used in CHF Congestive heart failure
Read important classifications :
Classification of drug used in CHF Congestive heart failure
1. Identification of infecting organism :
- It is important for selecting an appropriate antibiotics.
- Rapidly identified before treatment from body fluids.
2. Empirical therapy :
- An appropriate antimicrobial agent is used after receiving lab reports of identity and susceptibility except in case of acute illness.
3. Determination of Antimicrobial susceptibility :
This helps to determine the appropriate antimicrobial therapy.
4. Effect of site of infection :
- It is important for an antibiotic to reach appropriate site of action and in appropriate concentration in order to produce effective bactericidal or bacteriostatic effect - i.e. Eradicate the pathogen from site of infection.
- BBB offers challenge.
5. Patient factors :
Following needs to be considered before selecting Antibiotics :
- Host defense / how good is immune response of patient.
- Renal dysfunction.
- Hepatic dysfunction.
- Poor perfusion - i.e. blood supply to site of infection.
- Age.
- Pregnancy.
- Lactation.
6. Drug factors :
When any one of the number of drugs could be used to treat infection - then choice is based on specific properties of drug.
- Spectrum of activity.
- Type of effect required.
- Sensitivity of pathogen.
- Relative toxicity.
- Pharmacokinetics profile.
- Route of drug administration.
- Evidence of clinical efficacy.
PROBLEMS THAT ARISE WITH USE OF ANTIBIOTICS/ ADVERSE EFFECT
1. Toxicity :
a) local :- oral use - experienced at the site of administration - gastric irritation, pain.
Parentral use - abscess formation at the site of i.m injection, thromophelibitis.
b) systemic :- All antibiotics produce dose related and predictable organ toxocities.
- Some have high therapeutic index.
- Some have low therapeutic index.
Aminoglycosides : 8th cranial nerve, kidney toxicity.
Tetracyclines : liver and kidney damage.
Chloramphenicol : bone marrow depression.
Polymyxin : neurological and renal toxicity.
Amphotericin : kidney, bone marrow toxicity.
2. Hypersensitivity reaction / allergic reaction :
- All antibiotics are capable of causing hypersensitivity reactions.
- These are unpredictable and unrelated to dose.
- Anaphylactic shock can be produced.
- Penicillin allergy.
- A fungal infection especially after prolonged use of broad spectrum antibiotics.
- Difficult to treat due to alterations in the bormal microbial flora of gut, URT.
- Loss of sensitivity of pathogen to therapeutic effect of an antibiotics - to which it was previously sensitive.
- Developed by microorganisms when consistently exposed to sub therapeutic concentration of particular antibiotics.
- Some pathogens are naturally resistant to some antibiotics.
RESISTANCE DEVELOPMENT
1. Mutation : when insertion of one or more nucleotides within the genome. The mutated organism replicate with features that can be resist the action of an antibiotic.
2. Via R factors :
- Modification of target sites.
- Decreased accumulation of Antibiotic.
- By developing an inactivating enzyme which effectively destroys drug.
☆ You must have seen antibiotics given in combination, do you know why ? If not, continue, you will get to know.
WHY COMBINATION OF ANTIBIOTICS ?
1. To achieve synergism / additive effect :
- Synergistic effect sensitizes the organism to the action of the other member of pair.
- Rapid lethal action - than that of individual member separately.
- Prolonged post antibiotic effect. ( Aminoglycosides).
- Two bacteriostatic agents are often additive, sometimes synergistic, i.e. combination of tetracyclines, Chloramphenicol, Erythromycin etc.
- Two bactericidal drugs are frequently additivd if organism is sensitive ti both.
- Combination of a bactericidal with bacteriostatic drug may be synergistic or antagonistic depending on the organism.
2. To reduce severity or incidence of adverse effects :
- Possible only when combination is synergistic so that dose can be reduced.
- Especially when the antibiotics are if narrow therapeutic index - which when used alone in effective doses produce unacceptable toxicity.
- Streptomycin + Penicillin G for SABE.
3. To prevent emergence of resistance :
- This principle of using two or more AMAs together is valid primarily for chronic infections neeeding prolonged therapy; has been widely employed in tuberculosis, leprosy.
- Sulfonamides given with Streptomycin has been found to prevent emergence of resistant H. influenzae.
4. To broaden the spectrum of Antimicrobial action :
This is needed in :
- Treatment of mixed infection.
- Initial treatment of severe infection.
- Topically : generally AMAs which poorly absorbed from the local site, needs to given in combination.
TOP 10 ANTIBIOTICS
1. Ciprofloxacin
2. Ofloxacin
3. Amoxicillin
4. Streptomycin
5. Gentamycin
6. Neomycin
7. Erythromycin
8. Clindamycin
9. Norfloxacin
10. Levofloxacin
Ciprofloxacin : It is the most potent first generation Fluoroquinolone active against a broad range of bacteria.
- Ciprofloxacin is rapidly absorbed orally, but food delays absorption, and first pass metabolism occurs.
- High tissue penetrability.
- Excreted in urine.
- Adverse effects are - nausea, vomiting, anorexia, dizziness, headache, insomnia, rashes, swelling of lips. Side effects occur only in 10% patients.
Ofloxacin : It is more potent than Ciprofloxacin for gram positive organisms.
- Also inhibits M. Tuberculosis; can be used in place of ciprofloxacin.
- It is lipid soluble, bioavailability is high.
Amoxicillin :
- Oral absorption is good; food does not interfere.
- Higher and more sustained blood levels are produced.
Streptomycin : Oldest aminoglycoside antibiotic obtained from Streptomyces griseus.
- Active primarily against aerobic gram negative bacilli.
- Highly ionized, neither absorbed nor destroyed in g.i.t.
- Not metabolized - excreted unchanged in urine.
- Causes nephrotoxocity, hypertension, eosinophilia, rarely Anaphylaxis.
Gentamycin : obtained from Micromonospora purpurea in 1964 has become most commonly used antibiotic for acute infection.
Neomycin : obtained from S. fradiae, it is a wide spectrum aminoglycoside, active against most gram negative bacilli and some gram positive cocci.
- Highly toxic to internal ear and to kidneys.
- Poorly absorbed from g.i.t.
Clindamycin :
- It inhibits most gram positive cocci.
- Oral absorption is good, it penetrates to most skeletal and soft tissues, but not brain and CSF.
- Largely metabolized in urine and bile.
- Side effects are rashes, abdominal pain, major problem is diarrhoea.
Hello dear visitors
😊 I hope you've got help, if you have any suggestion or any question regarding this article"Antibiotics,, please comment i will be very happy.
Thanks
Also read : Congestive heart failure
ACE inhibitors
Antihypertensive drugs and classification
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