All of the following antibiotics are effectively used as antimicrobial agents after oral administration EXCEPT?
a. Amikacin
b. Cefaclor
c. Cephalexin
d. Amoxicillin
e. Azithromycin
The correct answer and explanation is:
The correct answer is a. Amikacin.
Amikacin is an aminoglycoside antibiotic, and it is generally not effective when taken orally. This is because it has poor absorption from the gastrointestinal tract. Aminoglycosides, including amikacin, are typically administered parenterally (via injection or intravenous infusion) to ensure they reach therapeutic levels in the bloodstream and are effective in treating infections, particularly those caused by gram-negative bacteria. Due to its poor oral bioavailability, amikacin is not used for oral administration.
In contrast, the other antibiotics listed have different mechanisms of action and are effectively absorbed when taken orally:
- Cefaclor is a second-generation cephalosporin antibiotic. It is well absorbed after oral administration and is used to treat various bacterial infections, including respiratory and urinary tract infections.
- Cephalexin is also a cephalosporin antibiotic, and it has good oral bioavailability. It is used for a wide range of bacterial infections, including skin, bone, and urinary tract infections.
- Amoxicillin is a broad-spectrum penicillin antibiotic that is well absorbed after oral administration. It is widely used for infections like ear infections, pneumonia, and strep throat.
- Azithromycin is a macrolide antibiotic that has high oral bioavailability and is commonly used to treat respiratory infections, sexually transmitted infections, and certain gastrointestinal infections.
To sum up, while the other antibiotics listed are suitable for oral administration, amikacin is not because it is poorly absorbed from the gastrointestinal tract and must be administered parenterally for effectiveness.