Cephradine is an antibiotic that belongs to a group of drugs called cephalosporins. Cephradine stops the bacteria from making their protein cell wall, so the bacteria die. Cephradine is used to treat bacterial infections of the respiratory tract, urinary tract, skin, and bone and joint. Cephradine is a broad-spectrum bacterial antibiotic active against both Gram-positive and Gram-negative bacteria. It is also highly active against most strains of penicillinase -producing staphylococci.
Cephradine is an oral first-generation cephalosporin antibiotic similar in structure and activity to cephalexin. The in vitro antibacterial activity of cephradine includes excellent gram-positive but limited gram-negative coverage. Cephradine is indicated for the treatment of urinary tract infections, skin and skin structure infections, respiratory tract infections, and otitis media. Cephradine has been administered parenterally, however, the parenteral product is no longer available in the United States.
Pharmacokinetics: Cephradine is administered orally. Following oral administration, the drug is rapidly and almost completely absorbed from the GI tract. In healthy patients, peak serum concentrations occur within 1 hour and average 9 mcg/ml following a single 250-mg dose, 15—18 mcg/ml after a single 500-mg dose, and 23.5—24.2 mcg/ml following a single 1-g dose. Administration with food lowers peak serum concentrations and Tmax; the total amount of drug absorbed is unchanged. Once in the systemic circulation, there is minimal binding (8—17%) to serum proteins. Cephradine does not cross the blood-brain barrier to any appreciable extent. Greater than 90% of the absorbed drug is excreted unchanged in the urine within 6 hours. Peak urine concentrations are approximately 1600 mcg/ml, 3200 mcg/ml, and 4000 mcg/ml following single doses of 250 mg, 500 mg, and 1 g, respectively. The elimination half-life is 1.3 hours in patients with normal renal function and 6—15 hours in patients with impaired renal function.
Mechanism of Action: Cephradine inhibits the third and final stage of bacterial cell wall synthesis by preferentially binding to specific penicillin-binding proteins (PBPs) located inside the bacterial cell wall. Penicillin-binding proteins are responsible for several steps in the synthesis of the cell wall and are found in quantities of several hundred to several thousand molecules per bacterial cell. Penicillin-binding proteins vary among different bacterial species. Thus, the intrinsic activity of cephradine as well as other cephalosporins and penicillins against a particular organism depends on their ability to gain access to and bind with the necessary PBP. Like all beta-lactam antibiotics, the ability of cephradine to interfere with PBP-mediated cell wall synthesis ultimately leads to cell lysis. Lysis is mediated by bacterial cell wall autolytic enzymes (i.e., autolysins). The relationship between PBPs and autolysins is unclear, but it is possible that the beta-lactam antibiotic interferes with an autolysin inhibitor. As a rule, first-generation cephalosporins are more active against gram-positive organisms than are second- and third-generation cephalosporins, but they have relatively little activity against gram-negative species. Gram-positive coverage includes nonpencillinase- and pencillinase-producing staphylococci (e.g., S. aureus) and streptococci (except enterococci). The gram-negative spectrum is limited to some strains Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis. Cephradine is inactive against enterococci (e.g., Enterococcus faecalis), methicillin-resistant staphylococci, Bacteroides fragilis, Citrobacter sp., Enterobacter sp., Listeria monoytogenes, Proteus sp. other than P. mirabilis, Providencia sp., Pseudomonas sp., and Serratia sp.
Cephradine is designated chemically as (6R,7R)-7-[(R)2-amino-2-(1,4-cyclohexadien-1-yl)acetamido]-3-methyl-8-oxo-5-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid.
It has the following molecular formula C16H19N3O4S with a molecular weight of 349.40.