Antibacterials penicillins

Beta-lactam antibiotics are a second great class of antibacterials penicillins, cephalosporins, carbapenems, and monobactams. They act by inhibiting bacterial cell wall synthesis. 

CO-fluampicil (Magnapen ) is an official name (UK) for a combination of equal parts of the broad-spectrum, ANTIBACTERIAL (penicillin) ANTIBIOTIC ampicillin and the penicillinase-resistant penicillin antibiotic and antibacterial flucloxacillin. Clinically, it can be used to treat severe... 

The name antibiotic was coined for substances isolated from microorganism growth media that had potent antibacterial, antifungal, antineo-plastic, and so on, activity. The well-known antibacterial penicillin G was the first to be discovered. Its activity was noted by Fleming in England in 1929, but the work of Florey and Chain in Oxford during... 

The macrolides such as erythromycin might possibly be expected to suppress the bacteria responsible for the enterohepatic recycling of ethinylestradiol, but good evidence that this is clinically important is scant (see Hormonal contraceptives + Antibacterials Penicillins , p.981). Erythromycin, and to a lesser extent the other macrolides discussed here, also inhibit the cytochrome P450 isoenzyme CYP3A4, which is responsible for the metabolism of the contraceptive steroids. Therefore they might be expected to increase rather than reduce contraceptive efficacy. This would be expected to offset any possible reduced enterohepatic recycling. 

The interaction between metronidazole and combined oral contraceptives is not established, and the whole issue of any interaction with broad-spectrum antibacterials remains very controversial. Bearing in mind the extremely wide use of both metronidazole and combined oral contraceptives, any increased incidence of contraceptive failure above that seen in general usage is clearly very low indeed. The Faculty of Family Planning and Reproductive Health Care (FFPRHC) Clinical Effectiveness Unit has issued guidance on the use of antibacterials with combined hormonal contraceptives. Although they recognise that there is poor evidence for contraceptive failure, they recommend that additional form of contraception, 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 metronidazole. ... 

The fluoroquinolones are broad-spectrum antibacterials, and so might be expected to interrupt the enterohepatic recirculation of ethinylestradiol, but the evidence that this is clinically important is scant (for a more detailed discussion of this mechanism see Hormonal contraceptives + Antibacterials Penicillins , p.981). 

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. 

Note that the mechanism behind the rare cases of failure of combined oral contraceptives seen with various broad-spectrum antibacterials is postulated to be reduced enterohepatic recycling of ethinylestradiol (see Hormonal contraceptives + Antibacterials Penicillins , p.981). Since progestagens are largely metabolised to inactive substances before they are conjugated, they do not undergo enterohepatic recycling of the active substance. 

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