Penicillin pharmacodynamics

Paton, Sir William, 2 Penicillin, 149, 150f Perospirone, 163f Pharmaceutics, 1, 169 Pharmacodynamics, 1—2, 163 Pharmacognosy, 1 Phar maco kinetics absorption, 163—164 clinical, 165... 

Schwank S, Blaser J. Once versus thrice-daily netilmicin combined with amoxicilUn, penicillin, or vancomycin against Enterococcus faecalis in a pharmacodynamic in vitro model. Antimicrob Agents Chemother 1996 40 2258-2261. 

Tobramycin is almost identical to gentamicin in both its pharmacodynamic and pharmacokinetic properties. However, it is much less active than either gentamicin or streptomycin when used in combination with a penicillin in the treatment of enterococcal endocarditis. The answer is (E). 

Not established. The pharmaeokinetie and pharmacodynamic evidence in-dieates that eo-trimoxazole is not likely to reduce the effectiveness of combined oral eontraeeptives. Although there are a number of reports of contraceptive failure attributed to co-trimoxazole, these are anecdotal and unconfirmed, whereas the studies suggest increased contraceptive efficacy (but see below). It is possible that the cases are coincidental, and fit within the normal failure rate of combined oral contraceptives. The UK Family Planning Authority considered that it was almost certain that co-trimoxazole and sulphonamides did not interact with combined oral contraceptives. However, the Faculty of Family Planning and Reproductive Health Care (FFPRHC) Clinical Effectiveness Unit has issued guidance on the use of antibacterials with hormonal contraceptives. Although they recognise that there is poor evidence for contraceptive failure, they recommend that additional contraceptives, such as condoms, should be used for short courses of antibacterials, see Hormonal contraceptives + Antibacterials Penicillins , p.981, for more detailed information. This applies to both the oral and the patch form of the combined contraceptive. This advice has usually been applied to only broad-spectrum antibacterials that do not induce liver enzymes but the FFPRHC notes that some confusion has occurred over which antibacterials are considered to be broad-spectrum , and thus they recommend that this advice is applied to all antibacterials that do not induce liver enzymes, which would include co-trimoxazole, sulfonamides and trimethoprim. ... 

The pharmacokinetics of a single 25-mg dose of doxylamine in 13 subjeets and the pharmacokinetics of a single 50-mg dose of diphenhydramine in 10 subjeets were not significantly altered by the use of low-dose eombined oral eontraceptives. Cases of oral contraceptive failure have been attributed to the use of doxylamine, chlorpheniramine, and an unnamed antihistamine, but these antihistamines were all used in con-junetion with penieillins, which would seem to be a more likely cause of contraceptive failure (see Hormonal contraceptives + Antibacterials Penicillins , p.981). The effect of the antihistamines on the pharmacokinetics and pharmacodynamics of contraceptive steroids appear not to have been studi. No particular precautions would seem necessary during concurrent use. 

LACTAM ANTIBIOTICS - deals with the chemical and biochemical aspects of the -lactam antibiotics. Topics selected include the synthesis, biosynthesis, chemical reactivity, anti-microbial activity, pharmacodynamics, metabolism, toxicology, detection and analysis, and pharmaceutical applications of the penicillins, cephalosporins, and related compounds. 

From these considerations, it might be concluded that the study of chemotherapy is immeasurably simpler than that of pharmacodynamics. However, those who study chemotherapy have to perform pharmacodynamic work also in order to follow the side effects of their drugs on the host. Even drugs, such as piperazine and penicillin, which have no side effects at all in the average patient, nevertheless need to be studied pharmacodynamically to discover their pattern of distribution in the body, and the origins of their favourable selectivity. 

---