#macrolides

Erythromycin

Clarithromycin Synonyms:A-56268, TE-031, 6-O-methylerythromycin, ATC:J01FA09Use:macrolide antibioticChemical name:6-O-methylerythromycinFormula:C38H69NO13 MW:747.96 g/molCAS-RN:81103-11-981103-11-9 klacid XL / Klaricid…

In this article, we will discuss Macrolides (Dosage). So, let’s get started. MacrolidesAzithromycin 10 mg/kg/day single dose empty stomach oral on day 1 and then 5 mg/kg/day during next 4 days. A single dose of 30 mg/kg can be given. Avoid administration in infants below 6 months. Enteric fever: 20 mg/kg/day for 7-14 days. Cholera: 20 mg/kg single dose.Adult dose: 500 mg once daily for 3 days;…

A new way to make powerful antibiotics

Macrolides, drugs that include erythromycin and azithromycin, were first developed in the 1950s. Since then they’ve become a bulwark against bacterial and fungal infections. Chemically, macrolides are giant rings containing 14 to 16 carbon atoms, with one or more sugar appendages dangling off the side. Bacteria synthesize them to fight off their neighbors. Yet bacteria didn’t evolve to make macrolides good drugs in people. So medicinal chemists—the group of researchers who actually build new drugs—start with the natural versions and tweak their bonds one at a time in an effort to make them safer and more effective. But in most cases it’s impossible to confine the changes to just one bond on a large molecule. When multiple bonds react, the result is an unwanted broad mixture of end products, none of which contain just the one specific change desired for making a better drug.  

To solve that problem, Harvard University chemist Andrew Myers and colleagues adapted a divide-and-conquer strategy that they had applied to tetracycline antibiotics back in 2005. They started with three basic macrolide ring structures and broke each one down into eight molecular “modules.” They then carefully mapped out reactions needed to put the pieces back together. For two such linkers they even invented new chemical reactions to forge the bonds just so. This allowed them to tinker with the modules individually, and then reassemble them. By repeating the strategy over and over, they forged more than 300 entirely new macrolides.

Strep throat, due to Streptoccocus pyogenes in the majority of cases. Other agents can be:  S. agalactiae, S. dysgalactiae subsp. equisimilis, S. pneumoniae and the S. mitis spp. group, S. anginosus spp. group, S. bovis spp. group, S. mutans spp. group, S. salivarius spp. group, and a handful of other Streptococci isolated from animals that may occasionally cause human infection. 

Most pharyngitis are viral, and the use of antibiotics are overly used, that is why the use of The  Modified Centor Criteria (or McIsaac Score) correlate directly with risk of positive throat culture for GAS and the empiric treatment with antibiotic. 

Criteria 

Guideline 

In patients with three or more Centor criteria a rapid antigen detection test without backup of throat culture fro negative results.

Throat culture has been considered the gold standard method to establish the microbial cause of acute pharyngitis. However, compared with RADT, cultures delay diagnosis as they take 24 to 48 hours to grow. Throat culture is primarily used as a backup test in patients with negative RADT where clinical concern for GAS or bacterial pharyngitis is still high.

Treatment guideline in the USA: 

Penicilin is the first line treatment, cephalosporins, macrolides, and clindamicyn. 

Adults                      

Oral penicillin V* (phenoxymethyl penicillin)

500 mg two to three times daily for 10 days

Amoxicillin

500 mg twice daily for 10 dayS

Intramuscular penicillin, single dose

Penicillin G benzathine (Bicillin L-A) 1.2 million units

Cephalexin

500 mg orally twice daily for 10 days25 to 50 mg/kg per day orally in two equally divided doses (maximum 1000 mg per day) for 10 days

For patients with potential severe hypersensitivity to beta-lactam antibiotics (eg, penicillin, cephalosporins):

Azithromycin

500 mg orally on day 1 followed by 250 mg orally on days 2 through 512 mg/kg/dose (maximum 500 mg/dose) orally on day 1 followed by 6 mg/kg/dose (maximum 250 mg/dose) orally on days 2 through 5

Clarithromycin

250 mg orally twice daily for 10 days7.5 mg/kg/dose (maximum 250 mg per dose) orally twice daily for 10 days

Clindamycin

300 mg orally three times daily for 10 days

Children and Adolescents: 

Oral penicillin V* (phenoxymethyl penicillin)

If ≤27 kg: 250 mg two to three times daily for 10 days

If >27 kg: 500 mg two to three times daily for 10 days

Amoxicillin

50 mg/kg per day orally (maximum 1000 mg per day) for 10 days. May be administered in two or three equally divided doses.

Intramuscular penicillin, single dose

If ≤27 kg: Penicillin G benzathine and penicillin G procaine (Bicillin C-R 900/300) 600,000 units. Consists of benzathine penicillin G 900,000 units mixed with procaine penicillin G 300,000 units.

If >27 kg: Penicillin G benzathine (Bicillin L-A) 1.2 million units

Cephalexin

25 to 50 mg/kg per day orally in two equally divided doses (maximum 1000 mg per day) for 10 days

For patients with potential severe hypersensitivity to beta-lactam antibiotics (eg, penicillin, cephalosporins):

Azithromycin

12 mg/kg/dose (maximum 500 mg/dose) orally on day 1 followed by 6 mg/kg/dose (maximum 250 mg/dose) orally on days 2 through 5

Clarithromycin

7.5 mg/kg/dose (maximum 250 mg per dose) orally twice daily for 10 days

Clindamycin

If ≤70 kg: 7 mg/kg/dose (maximum 300 mg per dose) orally three times daily for 10 days

If >70 kg: 300 mg orally three times daily for 10 days

Treatment guideline in Mexico: 

Amoxicilin with clavulanic acid 500 mg orally every 8 hours fro 10 days 

first generation cephalosporin for 10 days 

clindamicyn 600 mg/day in 2-4 dose fro 10 days 

Penicillin G procaine 1,200,000UI every 12 hours 2 doses, followed by 3 doses of penecillin G 800,000ui every 12 hours IM. 

in case of Penicillin allergy:

Erithromycine 500 mg every 12 hours for 10 days 

Cefalexin 250mg every 12 hours or cephadroxil 1 every 12 hrs 

tmp/smx 80/400mg 2 pills every 12 hours for 10 days 

In case of failure to response to treatment, to erradicate penicillin G is used, 1.200.000UI every 21 day for 3 months 

Prevention: