Pharmacokinetics of ampicillin and sulbactam in pregnancy

Ampicillin Pharmacokinetics in Peripartum and Laboring Women

OBJECTIVE

 Ampicillin is used for multiple peripartum indications including prevention of neonatal group B streptococcus (GBS) and treatment of chorioamnionitis. Despite its widespread use in obstetrics, existing pharmacokinetic data for ampicillin do not address contemporary indications or dosing paradigms for this population. We sought to characterize the pharmacokinetic profile of ampicillin administered to laboring women.

STUDY DESIGN

 Using whole blood dried blood spot sampling technique, maternal blood samples were collected at specified times from 31 women receiving intravenous (IV) ampicillin for peripartum indications. Women received either a 2-g loading dose with 1-g administered every 4 hours (GBS) or 2-g every 6 hours (chorioamnionitis). Pharmacokinetics were analyzed via a population approach with nonlinear mixed-effect modeling.

RESULTS

 The data were best described by a two-compartment model with first-order elimination, with the following whole blood parameters: central volume of distribution (V1), 75.2 L (95% confidence interval [CI]: 56.3-93.6); clearance (CL), 82.4 L/h (95% CI: 59.7-95.7); intercompartmental clearance (Q), 20.9 L/h (95% CI: 16.2-38.2); and peripheral volume of distribution (V2), 61.1 L (95% CI: 26.1-310.5). Interpatient variation in CL and V1 was large (42.0 and 56.7%, respectively). Simulations of standard dosing strategies demonstrated over 98% of women are predicted to achieve an estimated free plasma concentration above mean inhibitory concentration (MIC) of 0.5 μg/mL for more than 50% of the dosing interval.

CONCLUSION

 Although large variation in the pharmacokinetics of ampicillin in pregnant women exists, as predicted by our model, current standard dosing strategies achieve adequate exposure for GBS in nearly all patients.

KEY POINTS

· IV ampicillin is widely used in obstetrics.. · Pharmacokinetic studies are lacking.. · Ampicillin pharmacokinetics were established.. · Ampicillin clearance and volume of distribution are high.. · Current ampicillin dosing strategies are sufficient..

Pharmacokinetics and Target Attainment of Antimicrobial Drugs Throughout Pregnancy: Part I-Penicillins

BACKGROUND AND OBJECTIVE

Pharmacokinetics (PK) are severely altered in pregnant women due to changes in volume of distribution (Vd) and/or drug clearance (CL), affecting target attainment of antibiotics in pregnant women. This review is part of a series that reviews literature on the description of PK and target attainment of antibiotics in pregnant women with specific focus on penicillins.

METHODS

A systematic literature search was carried out in PubMed. Articles were labelled as relevant when information on PK of penicillins in pregnant women was available.

RESULTS

Thirty-two relevant articles were included, 8 of which discussed amoxicillin (with and without clavulanic acid), 15 ampicillin, 4 benzylpenicillin, 1 phenoxymethylpenicillin, and 4 piperacillin (with and without tazobactam). No studies were found on pheneticillin and flucloxacillin in pregnant women. Ten out of 32 articles included information on both Vd and CL. During the second and third trimester of pregnancy, a higher CL and larger Vd was reported than in non-pregnant women and in pregnant women during first trimester. Reduced target attainment was described in second and third trimester pregnant women. Only 7 studies reported dosing advice, 4 of which were for amoxicillin.

CONCLUSION

The larger Vd and higher CL in second and third trimester pregnant women might warrant a higher dosage or shortening of the dosing interval of penicillins to increase target attainment. Studies frequently fail to provide dosing advice for pregnant women, even if the necessary PK information was available.

Understanding the pharmacokinetics of antibiotics in pregnancy: Is there a role for therapeutic drug monitoring? A narrative review

PURPOSE

Antibiotics are commonly used during pregnancy. However, physiological changes during pregnancy can affect the pharmacokinetics of drugs, including antibiotics, used during this period. Pharmacokinetic evaluations have shed light on how antibiotics are affected during pregnancy and have influenced dosing recommendations in this context. Methods: A narrative review was conducted and included reports providing data reflecting drug distribution and exposure in the context of pregnancy. Results: Pharmacokinetic parameters of antibiotics in pregnancy and transplacental passage of antibiotics are comprehensively presented. Conclusion: Knowledge about the impact on pharmacokinetics and fetal exposure is especially helpful for complicated or severe infections, including intra-amniotic infection and sepsis in pregnancy, where both mother and fetus are at risk. Further studies are warranted to consolidate the role of therapeutic drug monitoring in complicated or severe infections in pregnant patients.

Different classes of antibiotics given to women routinely for preventing infection at caesarean section

BACKGROUND

Caesarean section increases the risk of postpartum infection for women and prophylactic antibiotics have been shown to reduce the incidence; however, there are adverse effects. It is important to identify the most effective class of antibiotics to use and those with the least adverse effects.  OBJECTIVES: To determine, from the best available evidence, the balance of benefits and harms between different classes of antibiotic given prophylactically to women undergoing caesarean section, considering their effectiveness in reducing infectious complications for women and adverse effects on both mother and infant.

SEARCH METHODS

For this 2020 update, we searched Cochrane Pregnancy and Childbirth's Trials Register, ClinicalTrials.gov, the WHO International Clinical Trials Registry Platform (ICTRP) (2 December 2019), and reference lists of retrieved studies.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) comparing different classes of prophylactic antibiotics given to women undergoing caesarean section.  RCTs published in abstract form were also included. We excluded trials that compared drugs with placebo or drugs within a specific class; these are assessed in other Cochrane Reviews. We excluded quasi-RCTs and cross-over trials. Cluster-RCTs were eligible for inclusion but none were identified.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed the studies for inclusion, assessed risk of bias and carried out data extraction. We assessed the certainty of the evidence using the GRADE approach.

MAIN RESULTS

We included 39 studies, with 33 providing data (8073 women). Thirty-two studies (7690 women) contributing data administered antibiotics systemically, while one study (383 women) used lavage and was analysed separately. We identified three main comparisons that addressed clinically important questions on antibiotics at caesarean section (all systemic administration), but we only found studies for one comparison, 'antistaphylococcal cephalosporins (1st and 2nd generation) versus broad spectrum penicillins plus betalactamase inhibitors'.   We found no studies for the following comparisons: 'antistaphylococcal cephalosporins (1st and 2nd generation) versus lincosamides' and 'antistaphylococcal cephalosporins (1st and 2nd generation) versus lincosamides plus aminoglycosides'. Twenty-seven studies (22 provided data) included comparisons of cephalosporins (only) versus penicillins (only). However for this update, we only pooled data relating to different sub-classes of penicillins and cephalosporins where they are known to have similar spectra of action against agents likely to cause infection at caesarean section. Eight trials, providing data on 1540 women, reported on our main comparison, 'antistaphylococcal cephalosporins (1st and 2nd generation) versus broad spectrum penicillins plus betalactamase inhibitors'. We found data on four other comparisons of cephalosporins (only) versus penicillins (only) using systemic administration: antistaphylococcal cephalosporins (1st and 2nd generation) versus non-antistaphylococcal penicillins (natural and broad spectrum) (9 studies, 3093 women); minimally antistaphylococcal cephalosporins (3rd generation) versus non-antistaphylococcal penicillins (natural and broad spectrum) (4 studies, 854 women); minimally antistaphylococcal cephalosporins (3rd generation) versus broad spectrum penicillins plus betalactamase inhibitors (2 studies, 865 women); and minimally antistaphylococcal cephalosporins (3rd generation) versus broad spectrum and antistaphylococcal penicillins (1 study, 200 women). For other comparisons of different classes of antibiotics, only a small number of trials provided data for each comparison, and in all but one case data were not pooled. For all comparisons, there was a lack of good quality data and important outcomes often included few women. Three of the studies that contributed data were undertaken with drug company funding, one was funded by the hospital, and for all other studies the funding source was not reported. Most of the studies were at unclear risk of selection bias, reporting bias and other biases, partly due to the inclusion of many older trials where trial reports did not provide sufficient methodological information. We undertook GRADE assessment on the only main comparison reported by the included studies, antistaphylococcal cephalosporins (1st and 2nd generation) versus broad spectrum penicillins plus betalactamase inhibitors, and the certainty ranged from low to very low, mostly due to concerns about risk of bias, wide confidence intervals (CI), and few events. In terms of the primary outcomes for our main comparison of 'antistaphylococcal cephalosporins (1st and 2nd generation) versus broad spectrum penicillins plus betalactamase inhibitors': only one small study reported sepsis, and there were too few events to identify clear differences between the drugs (risk ratio (RR) 2.37, 95% CI 0.10 to 56.41, 1 study, 75 women, very low-certainty evidence). There may be little or no difference between these antibiotics in preventing endometritis (RR 1.10; 95% CI 0.76 to 1.60, 7 studies, 1161 women; low-certainty evidence). None of the included studies reported on infant sepsis or infant oral thrush. For our secondary outcomes, we found there may be little or no difference between interventions for maternal fever (RR 1.07, 95% CI 0.65 to 1.75, 3 studies, 678 women; low-certainty evidence). We are uncertain of the effects on maternal: wound infection (RR 0.78, 95% CI 0.32 to 1.90, 4 studies, 543 women), urinary tract infection (average RR 0.64, 95% CI 0.11 to 3.73, 4 studies, 496 women), composite adverse effects (RR 0.96, 95% CI 0.09 to 10.50, 2 studies, 468 women), and skin rash (RR 1.08, 95% CI 0.28 to 4.1, 3 studies, 591 women) (all very low certainty evidence). Although maternal allergic reactions were reported by two studies, there were no events. There were no infant outcomes reported in the included studies. For the other comparisons, the results for most outcomes had wide CIs, few studies and few women included. None of the included trials reported on longer-term maternal outcomes, or on any infant outcomes.

AUTHORS' CONCLUSIONS

Based on the best currently available evidence, 'antistaphylococcal cephalosporins' and 'broad spectrum penicillins plus betalactamase inhibitors' may have similar efficacy at caesarean section when considering immediate postoperative infection, although we did not have clear evidence for several important outcomes. Most trials administered antibiotics at or after cord clamping, or post-operatively, so results may have limited applicability to current practice which generally favours administration prior to skin incision. We have no data on any infant outcomes, nor on late infections (up to 30 days) in the mother; these are important gaps in the evidence that warrant further research. Antimicrobial resistance is very important but more appropriately investigated by other trial designs.

Drug dosing during pregnancy-opportunities for physiologically based pharmacokinetic models

Drugs can have harmful effects on the embryo or the fetus at any point during pregnancy. Not all the damaging effects of intrauterine exposure to drugs are obvious at birth, some may only manifest later in life. Thus, drugs should be prescribed in pregnancy only if the expected benefit to the mother is thought to be greater than the risk to the fetus. Dosing of drugs during pregnancy is often empirically determined and based upon evidence from studies of non-pregnant subjects, which may lead to suboptimal dosing, particularly during the third trimester. This review collates examples of drugs with known recommendations for dose adjustment during pregnancy, in addition to providing an example of the potential use of PBPK models in dose adjustment recommendation during pregnancy within the context of drug-drug interactions. For many drugs, such as antidepressants and antiretroviral drugs, dose adjustment has been recommended based on pharmacokinetic studies demonstrating a reduction in drug concentrations. However, there is relatively limited (and sometimes inconsistent) information regarding the clinical impact of these pharmacokinetic changes during pregnancy and the effect of subsequent dose adjustments. Examples of using pregnancy PBPK models to predict feto-maternal drug exposures and their applications to facilitate and guide dose assessment throughout gestation are discussed.

A pharmacokinetic assessment of optimal dosing, preparation, and chronotherapy of aspirin in pregnancy

BACKGROUND

The benefit of aspirin in preventing preeclampsia is well established; however, studies over the years have demonstrated variability in outcomes with its use. Potential contributing factors to this variation in efficacy include dosing, time of dosing, and preparation of aspirin.

OBJECTIVE

We aimed to compare the difference in pharmacokinetics of aspirin, through its major active metabolite, salicylic acid, in pregnant women and nonpregnant women, and to examine the effect of dose (100 mg vs 150 mg), preparation (enteric coated vs non-enteric-coated), and chronotherapy of aspirin (morning vs evening) between the 2 groups.

MATERIALS AND METHODS

Twelve high-risk pregnant women and 3 nonpregnant women were enrolled in this study. Pregnant women were in 1 of 4 groups (100 mg enteric coated, 100 mg non-enteric-coated, 150 mg non-enteric-coated morning dosing, and 150 mg non-enteric-coated evening dosing), whereas nonpregnant women undertook each of the 4 dosing schedules with at least a 30-day washout period. Blood samples were collected at baseline (before ingestion) and at 1, 2, 4, 6, 12, and 24 hours after ingestion of aspirin. Plasma obtained was analyzed for salicylic acid levels by means of liquid chromatography-mass spectrometry. Pharmacokinetic values of area under the curve from time point 0 to 24 hours point of maximum concentration, time of maximum concentration, volume of distribution, clearance, and elimination half-life were analyzed for statistical significance with SPSS v25 software.

RESULTS

Pregnant women had a 40% ± 4% reduction in area under the curve from time point 0 to 24 hours (P < .01) and 29% ± 3% reduction in point of maximum concentration (P < .01) with a 44% ± 8% increase in clearance (P < .01) in comparison to that in nonpregnant women when 100 mg aspirin was administered. The reduction in the area under the curve from time point 0 to 24 hours, however, was minimized with the use of 150 mg aspirin in pregnant women, with which the area under the curve from time point 0 to 24 hours was closer to that achieved with the use of 100 mg aspirin in nonpregnant women. There was a 4-hour delay (P < .01) in the time of maximum concentration, a 47% ± 3% reduction in point of maximum concentration (P < .01) and a 48% ± 1% increase in volume of distribution (P < .01) with the use of 100 mg enteric-coated aspirin compared to non-enteric-coated aspirin, with no difference in the overall area under the curve. There was no difference in the pharmacokinetics of aspirin between morning and evening dosing.

CONCLUSION

There is a reduction in the total drug metabolite concentration of aspirin in pregnancy, and therefore a dose adjustment is potentially required in pregnant women. This is likely due to the altered pharmacokinetics of aspirin in pregnancy, with an increase in clearance. There was no difference in the total drug metabolite concentration of aspirin between enteric-coated and non-enteric-coated aspirin and between morning and evening dosing of aspirin. Further pharmacodynamic and clinical studies are required to examine the clinical relevance of these pharmacokinetic findings.

Pregnancy-Associated Changes in Pharmacokinetics: A Systematic Review

BACKGROUND

Women are commonly prescribed a variety of medications during pregnancy. As most organ systems are affected by the substantial anatomical and physiological changes that occur during pregnancy, it is expected that pharmacokinetics (PK) (absorption, distribution, metabolism, and excretion of drugs) would also be affected in ways that may necessitate changes in dosing schedules. The objective of this study was to systematically identify existing clinically relevant evidence on PK changes during pregnancy.

METHODS AND FINDINGS

Systematic searches were conducted in MEDLINE (Ovid), Embase (Ovid), Cochrane Central Register of Controlled Trials (Ovid), and Web of Science (Thomson Reuters), from database inception to August 31, 2015. An update of the search from September 1, 2015, to May 20, 2016, was performed, and relevant data were added to the present review. No language or date restrictions were applied. All publications of clinical PK studies involving a group of pregnant women with a comparison to nonpregnant participants or nonpregnant population data were eligible to be included in this review. A total of 198 studies involving 121 different medications fulfilled the inclusion criteria. In these studies, commonly investigated drug classes included antiretrovirals (54 studies), antiepileptic drugs (27 studies), antibiotics (23 studies), antimalarial drugs (22 studies), and cardiovascular drugs (17 studies). Overall, pregnancy-associated changes in PK parameters were often observed as consistent findings among many studies, particularly enhanced drug elimination and decreased exposure to total drugs (bound and unbound to plasma proteins) at a given dose. However, associated alterations in clinical responses and outcomes, or lack thereof, remain largely unknown.

CONCLUSION

This systematic review of pregnancy-associated PK changes identifies a significant gap between the accumulating knowledge of PK changes in pregnant women and our understanding of their clinical impact for both mother and fetus. It is essential for clinicians to be aware of these unique pregnancy-related changes in PK, and to critically examine their clinical implications.

Pharmacokinetics of drugs in pregnancy

Pregnancy is a complex state where changes in maternal physiology have evolved to favor the development and growth of the placenta and the fetus. These adaptations may affect preexisting disease or result in pregnancy-specific disorders. Similarly, variations in physiology may alter the pharmacokinetics or pharmacodynamics that determines drug dosing and effect. It follows that detailed pharmacologic information is required to adjust therapeutic treatment strategies during pregnancy. Understanding both pregnancy physiology and the gestation-specific pharmacology of different agents is necessary to achieve effective treatment and limit maternal and fetal risk. Unfortunately, most drug studies have excluded pregnant women based on often-mistaken concerns regarding fetal risk. Furthermore, over two-thirds of women receive prescription drugs while pregnant, with treatment and dosing strategies based on data from healthy male volunteers and non-pregnant women, and with little adjustment for the complex physiology of pregnancy and its unique disease states. This review will describe basic concepts in pharmacokinetics and their clinical relevance and highlight the variations in pregnancy that may impact the pharmacokinetic properties of medications.

Different classes of antibiotics given to women routinely for preventing infection at caesarean section

BACKGROUND

Caesarean section increases the risk of postpartum infection for women and prophylactic antibiotics have been shown to reduce the incidence; however, there are adverse effects. It is important to identify the most effective class of antibiotics to use and those with the least adverse effects.

OBJECTIVES

To determine, from the best available evidence, the balance of benefits and harms between different classes of antibiotic given prophylactically to women undergoing caesarean section.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (30 September 2014) and reference lists of retrieved papers.

SELECTION CRITERIA

We included randomised controlled trials comparing different classes of prophylactic antibiotics given to women undergoing caesarean section. We excluded trials that compared drugs with placebo or drugs within a specific class; these are assessed in other Cochrane reviews.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed the studies for inclusion, assessed risk of bias and carried out data extraction.

MAIN RESULTS

We included 35 studies of which 31 provided data on 7697 women. For the main comparison between cephalosporins versus penicillins, there were 30 studies of which 27 provided data on 7299 women. There was a lack of good quality data and important outcomes often included only small numbers of women.For the comparison of a single cephalosporin versus a single penicillin (Comparison 1 subgroup 1), we found no significant difference between these classes of antibiotics for our chosen most important seven outcomes namely: maternal sepsis - there were no women with sepsis in the two studies involving 346 women; maternal endometritis (risk ratio (RR) 1.11, 95% confidence interval (CI) 0.81 to 1.52, nine studies, 3130 women, random effects, moderate quality of the evidence); maternal wound infection (RR 0.83, 95% CI 0.38 to 1.81, nine studies, 1497 women, random effects, low quality of the evidence), maternal urinary tract infection (RR 1.48, 95% CI 0.89 to 2.48, seven studies, 1120 women, low quality of the evidence) and maternal composite adverse effects (RR 2.02, 95% CI 0.18 to 21.96, three studies, 1902 women, very low quality of the evidence). None of the included studies looked for infant sepsis nor infant oral thrush.This meant we could only conclude that the current evidence shows no overall difference between the different classes of antibiotics in terms of reducing maternal infections after caesarean sections. However, none of the studies reported on infections diagnosed after the initial postoperative hospital stay. We were unable to assess what impact, if any, the use of different classes of antibiotics might have on bacterial resistance.

AUTHORS' CONCLUSIONS

Based on the best currently available evidence, cephalosporins and penicillins have similar efficacy at caesarean section when considering immediate postoperative infections. We have no data for outcomes on the baby, nor on late infections (up to 30 days) in the mother. Clinicians need to consider bacterial resistance and women's individual circumstances.

Prophylaxis and treatment of anthrax in pregnant women

OBJECTIVE

To review the safety and pharmacokinetics of antimicrobials recommended for anthrax postexposure prophylaxis and treatment in pregnant women.

DATA SOURCES

Articles were identified in the PubMed database from inception through December 2012 by searching the keywords (["pregnancy]" and [generic antibiotic drug name]). Additionally, we searched clinicaltrials.gov and conducted hand searches of references from REPROTOX, TERIS, review articles, and Briggs' Drugs in Pregnancy and Lactation.

METHODS OF STUDY SELECTION

Articles included in the review contain primary data related to the safety and pharmacokinetics among pregnant women of 14 antimicrobials recommended for anthrax postexposure prophylaxis and treatment (amoxicillin, ampicillin, chloramphenicol, clindamycin, ciprofloxacin, doripenem, doxycycline, levofloxacin, linezolid, meropenem, moxifloxacin, penicillin, rifampin, and vancomycin).

TABULATION, INTEGRATION, AND RESULTS

The PubMed search identified 3,850 articles for review. Reference hand searching yielded nine additional articles. In total, 112 articles met the inclusion criteria.

CONCLUSIONS

Overall, safety and pharmacokinetic information is limited for these antimicrobials. Although small increases in risks for certain anomalies have been observed with some antimicrobials recommended for prophylaxis and treatment of anthrax, the absolute risk of these antimicrobials appears low. Given the high morbidity and mortality associated with anthrax, antimicrobials should be dosed appropriately to ensure that antibiotic levels can be achieved and sustained. Dosing adjustments may be necessary for the β-lactam antimicrobials and the fluoroquinolones to achieve therapeutic levels in pregnant women. Data indicate that the β-lactam antimicrobials, the fluoroquinolones, and, to a lesser extent, clindamycin enter the fetal compartment, an important consideration in the treatment of anthrax, because these antimicrobials may provide additional fetal benefit in the second and third trimesters of pregnancy.

Hollow-fiber pharmacodynamic studies and mathematical modeling to predict the efficacy of amoxicillin for anthrax postexposure prophylaxis in pregnant women and children

Amoxicillin is considered an option for postexposure prophylaxis of Bacillus anthracis in pregnant and postpartum women who are breastfeeding and in children because of the potential toxicities of ciprofloxacin and doxycycline to the fetus and child. The amoxicillin regimen that effectively kills B. anthracis and prevents resistance is unknown. Fourteen-day dose range and dose fractionation studies were conducted in in vitro pharmacodynamic models to identify the exposure intensity and pharmacodynamic index of amoxicillin that are linked with optimized killing of B. anthracis and resistance prevention. Studies with dicloxacillin, a drug resistant to B. anthracis beta-lactamase, evaluated the role of beta-lactamase production in the pharmacodynamic indices for B. anthracis killing and resistance prevention. Dose fractionation studies showed that trough/MIC and not time above MIC was the index for amoxicillin that was linked to successful outcome through resistance prevention. Failure of amoxicillin regimens was due to inducible or stable high level expression of beta-lactamases. Studies with dicloxacillin demonstrated that a time above MIC of ≥94% was linked with treatment success when B. anthracis beta-lactamase activity was negated. Recursive partitioning analysis showed that amoxicillin regimens that produced peak concentrations of <10.99 μg/ml and troughs of >1.75 μg/ml provided a 100% success rate. Other amoxicillin peak and trough values produced success rates of 28 to 67%. For postpartum and pregnant women and children, Monte Carlo simulations predicted success rates for amoxicillin at 1 g every 8 h (q8h) of 53, 33, and 44% (30 mg/kg q8h), respectively. We conclude that amoxicillin is suboptimal for postexposure prophylaxis of B. anthracis in pregnant and postpartum women and in children.

Drug metabolism and transport during pregnancy: how does drug disposition change during pregnancy and what are the mechanisms that cause such changes?

There is increasing evidence that pregnancy alters the function of drug-metabolizing enzymes and drug transporters in a gestational-stage and tissue-specific manner. In vivo probe studies have shown that the activity of several hepatic cytochrome P450 enzymes, such as CYP2D6 and CYP3A4, is increased during pregnancy, whereas the activity of others, such as CYP1A2, is decreased. The activity of some renal transporters, including organic cation transporter and P-glycoprotein, also appears to be increased during pregnancy. Although much has been learned, significant gaps still exist in our understanding of the spectrum of drug metabolism and transport genes affected, gestational age-dependent changes in the activity of encoded drug metabolizing and transporting processes, and the mechanisms of pregnancy-induced alterations. In this issue of Drug Metabolism and Disposition, a series of articles is presented that address the predictability, mechanisms, and magnitude of changes in drug metabolism and transport processes during pregnancy. The articles highlight state-of-the-art approaches to studying mechanisms of changes in drug disposition during pregnancy, and illustrate the use and integration of data from in vitro models, animal studies, and human clinical studies. The findings presented show the complex inter-relationships between multiple regulators of drug metabolism and transport genes, such as estrogens, progesterone, and growth hormone, and their effects on enzyme and transporter expression in different tissues. The studies provide the impetus for a mechanism- and evidence-based approach to optimally managing drug therapies during pregnancy and improving treatment outcomes.

When one drug affects 2 patients: a review of medication for the management of nonlabor-related pain, sedation, infection, and hypertension in the hospitalized pregnant patient

One of the most difficult challenges health care providers encounter is drug selection for pregnant patients. Drug selection can be complex as efficacy and maternal side effects must be weighed against potential risk to the embryo or fetus. Verification of an individual drug's fetal safety is limited as most evidence is deduced from epidemiologic, prospective cohort, or case-control studies. Medication selection for the pregnant inpatient is a particularly complex task as the illnesses and conditions that require hospitalization mandate different medications, and the risk versus benefit ratio can vary significantly compared to the outpatient setting. Some degree of acute pain is not uncommon among inpatients. Acetaminophen is generally considered the drug of choice in pregnancy for mild to moderate acute pain, while most opioids are thought to be safe for short-term use to manage moderate to severe pain. Providing sedation is particularly challenging as the few options available for the general population are further limited by either known increased risk of congenital malformations or very limited human pregnancy data. Propofol is the only agent recommended for continuous sedation, which has a Food and Drug Administration classification as a pregnancy category B medication. Treatment of infections in hospitalized patients requires balancing the microbiology profile against the fetal risk. Older antimicrobials proven generally safe include beta-lactams, and those with proven fetal risks include tetracyclines. However, little to no information regarding gestational use is available on the newer antimicrobials that are frequently employed to treat resistant infections more commonly found in the inpatient setting. Management of maternal blood pressure is based on the severity of blood pressure elevations and not the hypertensive classification. Agents generally considered safe to use in hypertensive pregnant patients include methyldopa, labetolol, and hydralazine, while angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, hydrochlorothiazide, and atenolol should be avoided.

Effect of pregnancy on topiramate pharmacokinetics in rabbits

Pregnancy is associated with various physiological changes that may lead to significant alterations in the pharmacokinetic profiles of many drugs. The present study was designed to investigate the potential effects of pregnancy on the pharmacokinetics of topiramate (TPM) in the rabbit model. Nineteen female New Zealand white rabbits (nine pregnant and 10 non-pregnant) were used in this study. Blood samples were collected from the animals just before receiving TPM orally at a dose of 20 mg/kg and then serially for up to 24 h. TPM plasma samples were analysed using a validated tandem mass spectrometric (LC-MS/MS) method. The mean values of TPM pharmacokinetic parameters (t(1/2), T(max), AUC(0-∞), and CL/F) were significantly modified in pregnant rabbits as compared with non-pregnant group. Pregnancy significantly (P < 0.05) increased TPM half-life (t(1/2)), time to attain the maximum plasma concentration (T(max)), and the area under TPM plasma concentration-time curve (AUC(0-∞)) and decreased the drug's oral clearance (CL/F) compared with non-pregnancy state in rabbits. The present study demonstrates that pregnancy alters the pharmacokinetics of TPM in rabbits in late gestational period and considerable inter-animal variability was observed. The findings of the present study indicate that TPM CL/F is decreased during late pregnancy in the rabbit model.

Different classes of antibiotics given to women routinely for preventing infection at caesarean section

BACKGROUND

Caesarean section increases the risk of postpartum infection for women and prophylactic antibiotics have been shown to reduce the incidence; however, there are adverse effects. It is important to identify the most effective class of antibiotics to use and those with the least adverse effects.

OBJECTIVES

To determine, from the best available evidence, the balance of benefits and harms between different classes of antibiotic given prophylactically to women undergoing caesarean section.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (April 2010) and reference lists of retrieved papers.

SELECTION CRITERIA

We included randomised controlled trials comparing different classes of prophylactic antibiotics given to women undergoing caesarean section. We excluded trials that compared drugs with placebo or drugs within a specific class; these are assessed in other Cochrane Reviews.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed the studies for inclusion, assessed risk of bias and carried out data extraction.

MAIN RESULTS

We included 29 studies of which 25 provided data on 6367 women. There was a lack of good quality data and important outcomes often included only small numbers of women. This meant we could only conclude that the current evidence shows no overall difference between the different classes of antibiotics in terms of reducing maternal infections after caesarean sections. However, none of the studies looked at outcomes on the baby, nor did they report infections diagnosed after the initial postoperative hospital stay. We were unable to assess what impact, if any, the use of different classes of antibiotics might have on bacterial resistance.

AUTHORS' CONCLUSIONS

Based on the best currently available evidence, cephalosporins and penicillins have similar efficacy at caesarean section when considering immediate postoperative infections. We have no data for outcomes on the baby, nor on late infections (up to 30 days) in the mother. Clinicians need to consider bacterial resistance and women's individual circumstances.

Ampicillin-sulbactam: an update on the use of parenteral and oral forms in bacterial infections

Ampicillin-sulbactam has a wide range of antibacterial activity that includes Gram-positive and Gram-negative aerobic and anaerobic bacteria. However, the drug is not active against Pseudomonas aeruginosa and pathogens producing extended-spectrum beta-lactamases. The combination could be considered particularly active against Acinetobacter baumannii infections due to the intrinsic activity of sulbactam. The drug is indicated as empirical therapy for a broad range of community acquired infections supervened in adults or children and is effective in either parenteral (ampicillin-sulbactam) or oral (as a mutual prodrug sultamicillin) form. In clinical trials, sultamicillin has proved clinically and bacteriologically effective in adults and children against a variety of frequently encountered infections, including mild upper and lower respiratory tract infections, urinary tract infections, diabetic foot and skin and soft tissue infections. Furthermore, adverse effects rarely occur with the diarrhoea to represent the most commonly reported. The parenteral ampicillin-sulbactam is indicated for community infections of mild-to-moderate severity acquired infections such as intra-abdominal or gynecological. Moreover, it seems to represent the alternative of choice for the treatment of A. baumannii infections for carbapenem-resistant strains in the nosocomial setting. Thus, ampicillin-sulbactam remains a valuable agent in the physician's armamentarium in the management of adult and pediatric infections.

The influence of labour on the pharmacokinetics of intravenously administered amoxicillin in pregnant women

AIMS

Many physiological changes take place during pregnancy and labour. These might change the pharmacokinetics of amoxicillin, necessitating adjustment of the dose for prevention of neonatal infections. We investigated the influence of labour on the pharmacokinetics of amoxicillin.

METHODS

Pregnant women before and during labour were recruited and treated with amoxicillin intravenously. A postpartum dose was offered. Blood samples were obtained and amoxicillin concentrations were determined using high-pressure liquid chromatography. The pharmacokinetics were characterized by nonlinear mixed-effects modelling using NONMEM.

RESULTS

The pharmacokinetics of amoxicillin in 34 patients was best described by a three-compartment model. Moderate interindividual variability was identified in CL, central and peripheral volumes of distribution. The volume of distribution (V) increased with an increasing amount of oedema. Labour influenced the parameter estimate of peripheral volume of distribution (V(2)). V(2) was decreased during labour, and even more in the immediate postpartum period. For all patients the population estimates (mean +/- SE) for CL and V were 21.1 +/- 4.1 l h(-1) (CL), 8.7 +/- 6.6 l (V(1)), 11.8 +/- 7.7 l (V(2)) and 20.5 +/- 15.4 l (V(3)) respectively.

CONCLUSIONS

The peripheral distribution volume of amoxicillin in pregnant women during labour and immediately postpartum is decreased. However, these changes are not clinically relevant and do not warrant deviations from the recommended dosing regimen for amoxicillin during labour in healthy pregnant patients.

Amoxicillin pharmacokinetics in pregnant women with preterm premature rupture of the membranes

OBJECTIVE

This study was undertaken to study the pharmacokinetics of intravenously administered amoxicillin in pregnant women with preterm premature rupture of the membranes (PPROM).

STUDY DESIGN

Healthy women with PPROM were recruited and treated with amoxicillin (2 g initially and 1 g subsequently). Blood samples were obtained from the opposite arm and concentrations determined with the use of high-pressure liquid chromatography. Nonlinear mixed-effects modeling was performed in nonlinear mixed effect (population) modeling.

RESULTS

The pharmacokinetics of 17 patients was described by a 3-compartment model. Clearance and volume of distribution at steady state were 22.8 L/h and 21.4 L/h, respectively, similar to values in nonpregnant individuals. There was little variability between patients. No relationship was observed between values of individual pharmacokinetic parameters and various covariates.

CONCLUSION

The pharmacokinetics of amoxicillin in pregnant patients with PPROM similar to nonpregnant individuals. Given the small interindividual variability in pharmacokinetics, no dose adjustments are required to account for differences between subjects under normal circumstances.

Using pharmacokinetics to predict the effects of pregnancy and maternal-infant transfer of drugs during lactation

Knowledge of pharmacokinetics and the use of a mechanistic-based approach can improve our ability to predict the effects of pregnancy for medications when data are limited. Despite the many physiological changes that occur during pregnancy that could theoretically affect absorption, bioavailability does not appear to be altered. Decreased albumin and alpha(1)-acid glycoprotein concentrations during pregnancy will result in decreased protein binding for highly bound drugs. For drugs metabolised by the liver, this can result in misinterpretation of total plasma concentrations of low extraction ratio drugs and overdosing of high extraction ratio drugs administered by non-oral routes. Renal clearance and the activity of the CYP isozymes, CYP3A4, 2D6 and 2C9, and uridine 5'-diphosphate glucuronosyltransferase are increased during pregnancy. In contrast, CYP1A2 and 2C19 activity is decreased. The dose of a drug an infant receives during breastfeeding is dependent on the amount excreted into the breast milk, the daily volume of milk ingested and the average plasma concentration of the mother. The lipophilicity, protein binding and ionisation properties of a drug will determine how much is excreted into the breast milk. The milk to plasma concentration ratio has large inter- and intrasubject variability and is often not known. In contrast, protein binding is usually known. An extensive literature review was done to identify case reports including infant concentrations from breast-fed infants exposed to maternal drugs. For drugs that were at least 85% protein bound, measurable concentrations of drug in the infant did not occur if there was no placental exposure immediately prior to or during delivery. Knowledge of the protein binding properties of a drug can provide a quick and easy tool to estimate exposure of an infant to medication from breastfeeding.

Pregnancy-induced changes in pharmacokinetics: a mechanistic-based approach

Observational studies have documented that women take a variety of medications during pregnancy. It is well known that pregnancy can induce changes in the plasma concentrations of some drugs. The use of mechanistic-based approaches to drug interactions has significantly increased our ability to predict clinically significant drug interactions and improve clinical care. This same method can also be used to improve our understanding regarding the effect of pregnancy on pharmacokinetics of drugs. Limited studies suggest bioavailability of drugs is not altered during pregnancy. Increased plasma volume and protein binding changes can alter the apparent volume of distribution (Vd) of drugs. Through changes in Vd and clearance, pregnancy can cause increases or decreases in the terminal elimination half-life of drugs. Depending on whether a drug is excreted unchanged by the kidneys or which metabolic isoenzyme is involved in the metabolism of a drug can determine whether or not a change in dosage is needed during pregnancy. The renal excretion of unchanged drugs is increased during pregnancy. The metabolism of drugs catalysed by select cytochrome P450 (CYP) isoenzymes (i.e. CYP3A4, CYP2D6 and CYP2C9) and uridine diphosphate glucuronosyltransferase (UGT) isoenzymes (i.e. UGT1A4 and UGT2B7) are increased during pregnancy. Dosages of drugs predominantly metabolised by these isoenzymes or excreted by the kidneys unchanged may need to be increased during pregnancy in order to avoid loss of efficacy. In contrast, CYP1A2 and CYP2C19 activity is decreased during pregnancy, suggesting that dosage reductions may be needed to minimise potential toxicity of their substrates. There are limitations to the available data. This analysis is based primarily on observational studies, many including small numbers of women. For some isoenzymes, the effect of pregnancy on only one drug has been evaluated. The full-time course of pharmacokinetic changes during pregnancy is often not studied. The effect of pregnancy on transport proteins is unknown. Drugs eliminated by non-CYP or non-UGT pathways or multiple pathways will need to be evaluated individually. In conclusion, by evaluating the pharmacokinetic data of a variety of drugs during pregnancy and using a mechanistic-based approach, we can start to predict the effect of pregnancy for a large number of clinically used drugs. However, because of the limitations, more clinical, evidence-based studies are needed to fully elucidate the effects of pregnancy on the pharmacokinetics of drugs.

Evidence on antibiotic prophylaxis for cesarean section alone is not sufficient to change the practices of doctors in a teaching hospital

AIMS

To assess the pattern of prophylactic antibiotic use in cesarean sections, identify factors associated with single-dose prescriptions as evidence-based best practice, and evaluate the changes in use of single-dose compared with multiple-dose regimens and the variation of use between doctors after dissemination of evidence.

METHODS

An analytical descriptive study was conducted. The medical records of 432 women undergoing cesarean section from April to September 2001 after dissemination of evidence in a teaching hospital in Southern Thailand were reviewed. Use of single-dose prophylactic antibiotic was the main outcome measure. Patterns of prophylactic antibiotics, and factors associated with pregnant women and doctors, were analyzed and compared with baseline data among 463 women undergoing cesarean section in 1998. Multivariate logistic regression with random effects was used for analysis.

RESULTS

After the dissemination of evidence, the rate of single-dose prescriptions increased from 14.2 to 22.4% (P < 0.01), single-dose prescriptions decreased for patients who had experienced longer durations of ruptured membranes, and the timing of the administration of antibiotics improved, but multiple-dose and duration of postoperative prescriptions increased. The variation in prescribing antibiotics between doctors was significant (P < 0.001).

CONCLUSIONS

Knowledge of evidence alone does not improve practices uniformly. Consequently, other interventions are necessary to improve practices.

Prophylactic antibiotic prescription for cesarean section

OBJECTIVES

To assess the use of prophylactic antibiotics for cesarean section, and to identify factors associated with a doctor's intraoperative prescription.

DESIGN

A hospital-based, cross-sectional study.

STUDY PARTICIPANTS

All 967 medical records of women undergoing cesarean section from January 1998 to February 1999 in a university hospital, Southern Thailand.

MAIN MEASURES

Independent variables consisted of patient and doctor factors. The outcome variable was whether any antibiotics were given intraoperatively. Multivariate logistic regression with random effects was used to identify factors associated with the doctor's prescription.

RESULTS

Prophylactic antibiotics were prescribed in 82% of all patients. One hundred and eighty-eight patients (21%) received antibiotics postoperatively. Of the patients receiving intraoperative antibiotics after cord clamping, 8% received only a single dose and 53% received an additional postoperative prescription. The most commonly used antibiotic was ampicillin. Intraoperative prescription was significantly associated with longer duration of ruptured membranes, higher number of vaginal examinations and doctors' age. Doctors aged 30-39 years had three and seven times the likelihood of prescribing intraoperative antibiotics compared with their younger and older colleagues, respectively.

CONCLUSIONS

Administration of single-dose prescriptions was still an uncommon practice. Prophylaxis was given more commonly to patients with well known risks for infection, and was given by doctors aged 30-39 years.

Drugs in pregnancy. Pharmacokinetics in pregnancy

Pharmacokinetics describes the handling of a drug by the body - how the drug is absorbed, distributed and eliminated and how these processes determine plasma concentrations of the drug. Changes in maternal physiology during pregnancy influence pharmacokinetics, and this may have important sequelae for drug dosing, especially for drugs for which adverse effects occur at concentrations within, or just above, the therapeutic range. For many drugs absorption is decreased and elimination increased, thus tending to reduce plasma concentrations. There are, however, relatively few specific data on pharmacokinetics in pregnancy, compared to the non-gravid state, because of the obvious ethical issues surrounding studies during pregnancy. Most therapeutic guidelines are thus based on observational studies and basic principles.

Pharmacokinetic changes during pregnancy and their clinical relevance

The dynamic physiological changes that occur in the maternal-placental-fetal unit during pregnancy influence the pharmacokinetic processes of drug absorption, distribution and elimination. Pregnancy-induced maternal physiological changes may affect gastrointestinal function and hence drug absorption rates. Ventilatory changes may influence the pulmonary absorption of inhaled drugs. As the glomerular filtration rate usually increases during pregnancy, renal drug elimination is generally enhanced, whereas hepatic drug metabolism may increase, decrease or remain unchanged. A mean increase of 8 L in total body water alters drug distribution and results in decreased peak serum concentrations of many drugs. Decreased steady-state concentrations have been documented for many agents as a result of their increased clearance. Pregnancy-related hypoalbuminaemia, leading to decreased protein binding, results in increased free drug fraction. However, as more free drug is available for either hepatic biotransformation or renal excretion, the overall effect is an unaltered free drug concentration. Since the free drug concentration is responsible for drug effects, the above mentioned changes are probably of no clinical relevance. The placental and fetal capacity to metabolise drugs together with physiological factors, such as differences acid-base equilibrium of the mother versus the fetus, determine the fetal exposure to the drugs taken by the mother. As most drugs are excreted into the milk by passive diffusion, the drug concentration in milk is directly proportional to the corresponding concentration in maternal plasma. The milk to plasma (M:P) ratio, which compares milk with maternal plasma drug concentrations, serves as an index of the extent of drug excretion in the milk. For most drugs the amount ingested by the infant rarely attains therapeutic levels.

Ampicillin for neonatal group B streptococcal prophylaxis: how rapidly can bactericidal concentrations be achieved?

OBJECTIVE

Our purpose was to determine how rapidly bactericidal concentrations of ampicillin against group B streptococci are achieved in amniotic fluid and cord blood after a 2 gm maternal infusion.

STUDY DESIGN

Ampicillin was administered at varying time intervals between 3 and 67 minutes before elective cesarean delivery in 40 women. Samples of amniotic fluid were obtained by amniocentesis just before the uterine incision was made. Umbilical and maternal blood were obtained at the time of delivery. Ampicillin concentrations were measured by high-pressure liquid chromatography.

RESULTS

The mean concentrations of ampicillin measured in maternal and umbilical cord sera all exceeded the minimum bactericidal concentrations reported for group B streptococci (0.25 to 2.0 micrograms/ml) and were achieved as soon as 5 minutes after ampicillin infusion. Similarly, bactericidal levels of ampicillin in the amniotic fluid could be detected as early as 5 minutes. However, such concentrations of ampicillin in the amniotic fluid were achieved in only 85% of the pregnancies studied.

CONCLUSIONS

Bactericidal levels of ampicillin against group B streptococci can usually be achieved rapidly in both fetal blood and amniotic fluid after a standard 2 gm intravenous dose given to the mother for neonatal prophylaxis.

The effect of timing of single-dose transplacental ampicillin-sulbactam therapy for prevention of neonatal group B streptococcal colonization and bacteremia in a rabbit model

OBJECTIVE

Our purpose was to evaluate the effect of maternal administration of ampicillin-sulbactam on group B streptococcal colonization and bacteremia in newborn rabbits.

STUDY DESIGN

Before induction of labor, timed pregnant New Zealand White rabbits on day 29 of a 31-day gestation received no therapy or ampicillin-sulbactam 50 mg/kg intramuscularly as a single dose 2 to 8 hours before delivery. Labor was induced with oxytocin. After delivery, the oropharynx of each pup was inoculated with 10(9) cfu of type la group B Streptococcus. Cultures of each pup were taken from the oropharynx and anorectum daily and from the heart at death or after 96 hours. Ampicillin-sulbactam concentrations were determined at delivery in both mothers and pups.

RESULTS

Thirteen animals were assigned to no therapy and 14 animals to ampicillin-sulbactam. Untreated pups had 100% oropharyngeal colonization at 24 hours. Pups treated with antibiotic were significantly less likely to have positive oropharyngeal cultures at 24 and 48 hours after birth than did untreated pups (24 hours 47% vs 100%, p < 0.0001; 48 hours 68% vs 91%, p = 0.0006). For anorectal cultures treated pups were significantly less likely to have positive culture results. Heart cultures were also less likely to have positive results for treated animals at 48 and 72 hours than for untreated animals (48 hours 30% vs 96%, p = 0.0001; 72 hours 31% vs 71%, p = 0.03). Treated pups had higher rates of survival at 48 hours (89% vs 62%, p < 0.0001). When neonatal oropharyngeal colonization at 24 hours after birth was compared with length of time from maternal antibiotic injection to delivery, there was a significant polynomial relationship (r = 0.78, p < 0.05). Ampicillin-sulbactam serum concentrations were highest 3 to 5 hours after injection. An inverse relationship existed between the rate of neonatal oropharyngeal colonization with group B streptococci at 24 hours after birth and neonatal ampicillin serum concentrations near birth (r = 0.733).

CONCLUSION

Transplacental treatment with a single intramuscular dose of ampicillin-sulbactam significantly decreased neonatal colonization and bacteremia after oral inoculation with type la group B Streptococcus. An effect of ampicillin-sulbactam was evident as early as 2 hours but maximal 3 to 5 hours after injection.

Treatment of pregnant mice with antibiotics modulates the humoral response of the offspring: role of prenatal and postnatal factors

This study was designed to determine the role of prenatal and postnatal factors underlying altered humoral response of the offspring of mice treated with antibiotics during pregnancy. Pregnant random-bred NMRI mice were administered i.p. from the 11th to 15th day of pregnancy with a mixture of ampicillin and cloxacillin (2:1) in a daily dose of 21 mg/kg body weight. The litters of experimental and control mothers were cross-fostered at birth and the offspring were immunized on the 23rd or 24th postnatal day with SRBC. The primary humoral response was assayed using spectrophotometric determination of SRBC lysis mediated by anti-SRBC IgM antibodies produced by spleen cells. The offspring born of saline-treated mothers and transferred to mothers treated with antibiotics, as well as the offspring born to mothers treated with antibiotics and transferred to mothers treated with saline, produced significantly higher amounts of spleen anti-SRBC IgM than the control offspring. The results suggest that the immune response of the offspring was modulated by both the prenatally and postnatally acting factors, the latter being mediated by effects of antibiotics on the maternal organism.

Digoxigenin-ampicillin conjugate for detection of penicillin-binding proteins by chemiluminescence

This paper describes a highly sensitive new method for the identification of penicillin-binding proteins (PBPs) that is based on the use of an ampicillin-digoxigenin conjugate (DIG-AMP conjugate) which is detected by immunoblotting and chemiluminescence. The sensitivity of chemiluminescence permitted X-ray film exposure times to be decreased to minutes, as opposed to the days or weeks which are requisite when conventionally radiolabeled beta-lactams are used. Coupling of ampicillin to digoxigenin yielded a product containing digoxigenin (detected by chemiluminescence) which also was inhibitory for Staphylococcus aureus and Escherichia coli. Unconjugated digoxigenin at concentrations of up to 100 micrograms/ml was not inhibitory for either organism. For S. aureus the MICs of DIG-AMP (0.7 microgram of conjugated ampicillin per ml) and of free ampicillin (0.5 microgram/ml) were comparable, indicating that ampicillin retained its bioactivity when coupled to digoxigenin. However, for E. coli the MICs of DIG-AMP (70 micrograms of conjugated ampicillin per ml) and of free ampicillin (8 micrograms/ml) were widely disparate, suggesting that the DIG-AMP conjugate was too large and/or hydrophobic to traverse the E. coli outer membrane via porins. DIG-AMP binding assays with E. coli and S. aureus cell envelopes revealed profiles of PBPs similar to those detected with 125I-ampicillin or [3H]penicillin. DIG-AMP binding to PBPs was completely inhibited in competition experiments with free ampicillin or penicillin, supporting the specificity of the DIG-AMP conjugate for PBPs. DIG-AMP thus represents an advantageous alternative to radioactive beta-lactams for the identification and analysis of PBPs.