Cephalosporins and β-lactam Antibiotics

10 Questions

What is the primary reason for adding procaine to benzylpenicillin?

To reduce the pain and discomfort associated with intramuscular injection of penicillin

What is the duration of action of benzathine penicillin?

14 days or longer

Which of the following penicillins is effective against Gram-negative bacteria?

Ampicillin

What is the indication for using Penicillin G?

Syphilis, skin infections, meningitis, and rheumatic fever

Which generation of cephalosporins is active against most gram-positive cocci with minimal coverage against gram-negative bacteria?

First-generation

What is the use of cefazolin in surgical prophylaxis?

Cephalosporin of choice for surgical prophylaxis

Which of the following is a contraindication for using benzylpenicillin?

Hypersensitivity to penicillin

What is the mechanism of action of β-lactam antibiotics?

Inhibition of cell wall biosynthesis

Which of the following is a characteristic of benzathine penicillin?

Long-acting

What is the adverse effect of intramuscular injection of penicillin?

Pain and discomfort

Study Notes

Inhibitors of Cell Wall Biosynthesis: β-Lactam Antibiotics

β-lactam antibiotics include penicillins, cephalosporins, carbapenems, and monobactams.

Cephalosporins

Cephalosporins are contraindicated in patients with allergies to them or those who have had an anaphylactic reaction to penicillin or other beta-lactams.
Ceftriaxone is contraindicated in hyperbilirubinemic neonates and infants less than 28 days old who are expected to receive calcium-containing products.
Side effects of cephalosporins include pseudomembranous colitis, hypersensitivity reactions, and cross-reactivity with penicillin.
Cephalosporins have low toxicity and are generally safe.
Administration of cephalosporins: oral or parenteral for 1st, 2nd, and 3rd generations; parenteral for 5th generation; cefazolin and ceftriaxone have longer half-lives.

Generations of Cephalosporins

1st generation: e.g. cefazolin, cephapirin, cephradine; active against gram-positive cocci with minimal coverage against gram-negative bacteria.
2nd generation: e.g. cefuroxime; broader coverage against gram-negative bacteria.
3rd generation: e.g. ceftriaxone, ceftazidime; extended coverage against gram-negative bacteria, including Pseudomonas aeruginosa.
4th generation: e.g. cefepime; extended coverage against gram-negative bacteria, including Pseudomonas aeruginosa.
5th generation: e.g. ceftaroline; broad-spectrum antimicrobial covering susceptible gram-positive and gram-negative organisms, including MRSA, but not Pseudomonas aeruginosa.

Penicillins

Penicillins are active against gram-positive bacteria, with some members also effective against gram-negative bacteria.
Examples of orally effective penicillins: phenoxymethylpenicillin (penicillin V), oxacillin, cloxacillin, flucloxacillin, ampicillin, and amoxicillin.
Penicillin G is used to treat syphilis, skin infections, meningitis, and rheumatic fever.
Procaine benzylpenicillin is administered by deep intramuscular injection and is aimed at reducing pain and discomfort.
Benzathine penicillin is a long-acting penicillin injection that can remain in the blood for a detectable level for 14 days or longer.