Ampicillin dosing

Pharmacological Properties Ampicillin (principen, others) is well absorbed after oral administration. Intake of food prior to ampicillin ingestion diminishes absorption. Severe renal impairment markedly prolongs the tj of ampicilhn in the plasma. Peritoneal dialysis does not remove the drug from the blood, but hemodialysis removes -40% of the body store in 7 hours. Ampicillin doses must be decreased in the setting of renal dysfunction. Ampicilhn undergoes enterohepatic circulation and is excreted in appreciable quantities in the feces. 

The antibiotic of choice for group B streptococcal disease is penicillin G, although ampicillin is an alternative.43 No resistance to either agent has been reported, and their narrow spectrum of activity makes them ideal choices.43 Resistance has developed with the use of alternative choices for penicillin-allergic patients. A treatment algorithm for group B Streptococcus is shown in Fig. 44—3, and dosing recommendations are shown in Table 44-5. 

Ampicillin 150 mg/kg IV per day in divided doses every 8 hours 200 mg/kg IV per day in divided doses every 6-8 hours 300 mg/kg IV per day in divided doses every 6 hours... 

For enterococci, it is imperative to determine species and antibiotic susceptibilities. If the organism is susceptible to penicillin and vancomycin, treatment may consist of high-dose penicillin G, ampicillin, or vancomycin plus gentamicin (see Table 71-6). Treatment length is usually 4 to 6 weeks, with the aminoglycoside used over the entire course. As resistance develops to penicillin, ampicillin and vancomycin remain treatment options. Once the isolate becomes resistant to ampicillin, vancomycin is considered the treatment of choice. 

One excellent study [151] employed intravenous and oral dosing at each of several times postsurgery (1-2 weeks, 6 and 12 months). This design permits valid conclusions about the absorption process. There was a significant reduction after surgery in ampicillin absorption but no change in propylthiouracil absorption. 

Enterococcal endocarditis ordinarily requires 4 to 6 weeks of high-dose penicillin G or ampicillin, plus gentamicin for cure (Table 37-8). A 6-week course is recommended for patients with symptoms lasting longer than 3 months and those with PVE. 

Ampicillin sodium or 12 g/24 hours IV in six equally divided doses 4-6 IA Native valve 4-week therapy recommended for patients with symptoms of illness less than 3 months 6-week therapy... 

Vancomycin hydrochloride13, plus Gentamicin sulfate 30 m kg per 24 hours IV in 2 equally divided doses 6 IB Vancomycin therapy recommended only for patients unable to tolerate penicillin or ampicillin... 

In attempts to improve the oral activity of norfloxacin, prodrug techniques have been employed. In an initial approach, the (5-methyl-2-oxo-l,3-diox-4-yl)-methyl group, which had been shown previously to be effective in a novel ampicillin prodrug, was investigated as a promoiety [ 109]. However, although the ester (77) liberates norfloxacin in the presence of mouse blood, after oral administration to mice, it was found that the blood levels of norfloxacin achieved are lower (approximately with respect to Cmax) than those achieved upon oral administration of an equimolar dose of norfloxacin, itself. This observation has been assumed to be due to an instability of this ester prior to absorption rather than an inability to liberate the parent drug after absorption. 

A further example of the ability of doxycycline to penetrate into secretions is provided by a report [53] of a comparative trial of the drug and ampicillin in acute exacerbations in chronic bronchitis. It was found that 100 mg doxycycline daily and ampicillin 250 mg four times daily were clinically equally effective. Bacterio-logically, however, it was found that H. influenzae re-appeared in sputum more often during ampicillin therapy than y ith doxycycline. This was attributed, following earlier workers, to the failure of ampicillin (in the dose used) to reach adequate levels in sputum. By inference, therefore, doxycycline (at one tenth of the daily dosage) achieves adequate levels more readily. 

These examples were inappropriate. Overuse of ampicillin in medical practice was discussed by Wescoe on p. 27 of the FDA s own National Advisory Food and Drug Committee Report, on January 24, 1977. Wescoe said (speaking of antibiotics in animal feeds), "I really find it difficult to understand how you believe a hazard exists for instance, relative to Neisseria gonorrheae, where the disease is practically all human, where it has been treated worldwide for many years by ampicillin. .. and then strain to say that maybe that is in part due to subtherapeutic doses of the antibiotic in feed." Dr. Wescoe chaired the committee. 

Children 1 year of age or older (less than 40 kg) 300 mg/kg/day IV (200 mg ampicillin/100 mg sulbactam) in divided doses every 6 hours. 

In dental, oral, or upper respiratory tract procedures (alternate regimen) 1 to 2 g (50 mg/kg for children) ampicillin plus 1.5 mg/kg (2 mg/kg for children) gentamicin not to exceed 80 mg, both IM or IV % hour prior to procedure, followed by 1.5 g (25 mg/kg for children) amoxicillin 6 hours after initial dose or repeat parenteral dose 8 hours after initial dose. 

Penicillin is rapidly excreted by the kidneys small amounts are excreted by other routes. About 10% of renal excretion is by glomerular filtration and 90% by tubular secretion. The normal half-life of penicillin G is approximately 30 minutes in renal failure, it may be as long as 10 hours. Ampicillin and the extended-spectrum penicillins are secreted more slowly than penicillin G and have half-lives of 1 hour. For penicillins that are cleared by the kidney, the dose must be adjusted according to renal function, with approximately one fourth to one third the normal dose being administered if creatinine clearance is 10 mL/min or less (Table 43-1). 

Penicillins, for example, are cleared by preterm infants at 17% of the adult rate based on comparable surface area and 34% of the adult rate when adjusted for body weight. The dosage of ampicillin for a neonate less than 7 days old is 50-100 mg/kg/d in two doses at 12-hour intervals. The dosage for a neonate over 7 days old is 100-... 

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