GENERAL PRINCIPLES OF ANTIMICROBIAL THERAPY



GENERAL PRINCIPLES OF ANTIMICROBIAL THERAPY

Questions to ask before selecting an antibiotic:

Host factors:

1. Normal or abnormal immune status?
2. Underlying disease that will affect selection &/or dosing? (e.g. renal failure)
3. Seriousness of the infection?

Pathogen factors:

4. What are the most likely bugs based on the infection site?
5. Where was the infection acquired? (community or hospital setting?)
6. Local susceptibility patterns?

Drug factors:

7. Bioavailability at infected site? (e.g. blood-brain barrier)
8. Broad or narrow spectrum?
9. Bacteriocidal or bacteriostatic?
10. Side effect profile?

 General Principles:

1. Be elegant. Use the antibiotic with the narrowest spectrum that covers the pathogen.

2. Be smart. If a patient is very sick or immunocompromised, it’s OK to cover broadly for the first 1-3 days while you identify the pathogen as long as you narrow your choice as soon as possible.

3. Follow the 3 day rule: Broad spectrum antibiotics markedly alter the normal host flora about 3 days into therapy AND cultures should be back in 3 days so always reassess your antibiotic choices and narrow it when possible.

4. Assume nothing. If a patient needs IV antibiotics, then you need to make sure it is hanging within the time frame you determine reasonable.

5. New isn’t always better. When several antibiotics have similar coverage, select the least expensive.

 Antibiotic Classes by Coverage:

Gram positive coverage:

1. Penicillins (ampicillin, amoxicillin) penicillinase resistant (Dicloxacillin, Oxacillin)*
2. Cephalosporins (1st and 2nd generation)*
3. Macrolides (Erythromycin, Clarithromycin, Azithromycin)*
4. Quinolones (gatifloxacin, moxifloxacin, and less so levofloxacin)*
5. Vancomycin* (MRSA)
6. Sulfonamide/trimethoprim*(Increasing resistance limits use, very inexpensive)
7. Clindamycin*
8. Tetracyclines
9. Chloramphenicol (§causes aplastic anemia so rarely used)
10. Other: Linezolid, Synercid (VRE)

Gram negative coverage:

1. Broad spectrum penicillins (Ticarcillin-clavulanate, piperacillin-tazobactam)*
2. Cephalosporins (2nd, 3rd, and 4th generation)*
3. Aminoglycosides* (renal and ototoxicity)
4. Macrolides (Azithromycin)*
5. Quinolones (Ciprofloxacin)*
6. Monobactams (Azetreonam)*
7. Sulfonamide/trimethoprim*
8. Carbapenems (Imipenem)
9. Chloramphenicol§

Anaerobic coverage:

1. Metronidazole*
2. Clindamycin*
3. Broad spectrum penicillins*
4. Quinolones (Gatifloxacin, Moxifloxacin)
5. Carbapenems
6. Chloramphenicol§

Atypical coverage:

1. Macrolides (Legionella, Mycoplasma, chlamydiae)*
2. Tetracyclines (rickettsiae, chlamydiae)*
3. Quinolones (Legionella, Mycoplasma, Chlamydia)*
4. Chloramphenicol§ (rickettsiae, chlamydiae, mycoplasma)
5. Ampicillin (Listeria)

Pseudomonas coverage:

1. Ciprofloxacin
2. Aminoglycosides
3. Some 3rd generation cephalosporins
4. 4th generation cephalosporins
5. Broad spectrum penicillins
6. Carbapenems

Comments

Post a Comment

Popular posts from this blog

Skeletal muscle relaxants

Image
Skeletal muscle relaxants Physiology of SKM Contraction 1. Motor nerve impulse à 2. Release of ACh à 3. Binds with N M receptors at NMJ à 4. Depolarization & development of EPP at motor end plate (Mainly due to influx of Na + ) à 5. Muscle action potential (MAP) – contraction of SKM à 6. ACh is rapidly inactivated by ChE leading to repolarization à 7. Muscle is ready for a fresh nerve impulse. MECHANISM OF ACTION OF MUSCLE RELAXANTS Centrally acting muscle relaxants -           Reduce SKM tone by a selective action in the cerebrospinal axis, without altering consciousness. -           They selectively depress spinal and supraspinal polysynaptic reflexes involved in the regulation of muscle tone without significantly affecting monosynaptically mediated stretch reflex. -           Polysynaptic pathways in ascending reticula...
Read more

CNS Stimulants

CNS Stimulants The CNS stimulants are classified into three major categories a.        Cortical stimulants b.       Medullary stimulants c.        Spinal stimulants Cortical stimulants These are further divided into three types 1.        Classical cortical stimulants – Cocaine, Xanthines, Ephedrine and Amphetamine 2.        Psychotomimetics – Lysergic acid 3.        Antidepressants (Thymoleptics) – Imipramine , tranylcypramine and Isoniazid. Classical cortical stimulants ·          Cocaine, Amphetamine, Ephedrine and Xanthine are cortical stimulants. ·          These drugs affect mainly the sensory cortex but the motor cortex is also stimulated with high dose. Cocaine ·     ...
Read more

Pharmacokinetics - Drug absorption and Transport of drugs across biological membranes

Transport of drugs across biological membranes All pharmacokinetic processes involved transport of the drug across biological membranes. Biological Membrane Biological membranes may be viewed as mosaics of functional units composed of lipoprotein complex. Most membranes are composed of a fundamental structure called the unit membrane or plasma membrane. This boundary, which is 80 to 100 A° thick, surrounds single cell and nuclei. More complex barriers such as the intestinal epithelia and the skin are composed of multiples of this functional structure. The plasma membrane consists of a bilayer of amphipathic lipids with their hydrocarbon chains oriented inward to form a continuous hydrophobic phase and their hydrophilic heads oriented outward. Individual lipid molecules in the bilayer can move laterally, endowing the membrane with fluidity, flexibility, high electrical resistance and relative impermeability to highly polar molecules. The known fluidity of the phospholipids i...
Read more