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5.
1.
2.
1 Metabolic processes in the body
(1) Penicillins
PENs that can be absorbed orally include penicillin V, ampicillin , amoxicillin , oxacillin , cloxacillin , dicloxacillin, and flucloxacillin
.
Penicillin G cannot be taken orally, it is easily degraded by gastric acid and needs to be injected intramuscularly
PENs can bind to proteins: oxacillin belongs to the category with high protein binding rate, and the protein binding rate is greater than 90%; while penicillin and ticarcillin belong to the category with medium protein binding rate, and the protein binding rate is about 60%; and aminopenicillin , Piperacillin, mezlocillin, etc.
are categories with low protein binding rate, and the protein binding rate is about 20%
.
(2) Cephalosporins
Cephalexin is quickly and safely absorbed orally, and has a low protein binding rate in the body.
After absorption, it is widely distributed in tissues.
The concentration in kidney and liver is the highest.
The concentration in bile is 1 to 4 times that of serum
.
It is not metabolized in the body, can penetrate the placental barrier, can reach the highest blood concentration in synovial fluid and pericardial fluid, and is mainly excreted through the kidneys as a prototype
The biotransformation of ceftiofur in animals is mainly to remove the thiofuran carbonyl group at position 3 to produce defuroyl ceftiofur
.
Defuroyl ceftiofur has a complete β-lactam ring and exists in the form of its conjugate, maintaining antibacterial activity similar to ceftiofur
Metabolism studies of radiolabeled cefquinome in cattle, pigs, horses and dogs showed that only the original drug of cefquinome was detected in various metabolic pathways, and no other metabolites were detected
.
5.
1.
2.
2 Toxicology and adverse reactions
(1) Penicillins
PENs have no obvious toxicity and are the antibiotics with the largest chemotherapy index
.
However, if high-dose intravenous drip or intrathecal administration, too high concentration of the cerebrospinal fluid drug can cause convulsions, muscle clonus, and severe mental symptoms
Allergic reactions to PENs are more common, ranking first among various drugs
.
Penicillin allergic reactions include immediate allergic reactions and delayed allergic reactions.
(2) Cephalosporins
Allergic reactions are the most dangerous adverse reactions of CEPs, with an incidence rate of 0.
5% to 10% reported in the literature
.
The main clinical manifestations are skin rash, urticaria, drug eruption and eosinophilia, drug fever, and asthma.
Related links: Physical and chemical properties and uses of β-lactam drugs (2)
