Cephalosporins, specific agents

After a 1-g intravenous infusion, serum levels are 75-125 mcg/mL for most second-generation cephalosporins. Intramuscular administration is painful and should be avoided. Doses and dosing intervals vary depending on the specific agent (Table 43-2). There are marked differences in half-life, protein binding, and interval between doses. All are renally cleared and require dosage adjustment in renal failure. 

Second-generation cephalosporins are not as well absorbed orally as the first-generation cephalosporins, have a greater incidence of gastrointestinal adverse effects, and are more expensive than first-generation agents - thus they should only be used where specifically indicated. 

It is probable that the largest number of medicinally directed semi-synthetic agents ever produced containing a specific pharmacophore, the -lactam ring, are the penicillins, cephalosporins and mono-bactams. To these must also be added the synthetic cephems and cephams and the many variations upon those basic themes. Although current figures are not available, it was estimated in 1980 that over 10000 variations on the basic penicillin structure had been made and assayed for their ability to inhibit microbial growth (Hoover, J.R.E., personal communication). 

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