The binding of drugs to major human milk whey proteins

Drugs in Lactation

One impediment to breastfeeding is the lack of information on the use of many drugs during lactation, especially newer ones. The principles of drug passage into breastmilk are well established, but have often not been optimally applied prospectively. Commonly used preclinical rodent models for determining drug excretion into milk are very unreliable because of marked differences in milk composition and transporters compared to those of humans. Measurement of drug concentrations in humans remains the gold standard, but computer modeling is promising. New FDA labeling requirements present an opportunity to apply modeling to preclinical drug development in place of conventional animal testing for drug excretion into breastmilk, which should improve the use of medications in nursing mothers.

Modeling drug passage into human milk

Breastfeeding has positive health consequences for both the breastfed infant and the nursing mother.(1,2) Although information on drug use during lactation is available through sites such as LactMed,(3) available information is often incomplete. Unlike pregnancy, in which large numbers of pregnant women need to be studied to assure safety, measurement of drug concentrations in breastmilk in a relatively few subjects can provide valuable information to assess drug safety. This article reviews methods of measuring and predicting drug passage into breastmilk.

A comparative study on relieving post-episiotomy pain with diclofenac and indomethacin suppositories or placebo

In this study, we compare the prophylactic efficacy of a diclofenac suppository and an indomethacin suppository on decreasing post-episiotomy pain. A total of 90 women with 2nd-degree episiotomy were assigned to receive a single dose of diclofenac suppository (30), indomethacin suppository (30) or placebo (30), according to randomised blocks. The pain was assessed at 1, 2, 4, 6 and 12 hours after receiving analgesia, using the two methods of pain score and visual analogue. This study showed that in the group given diclofenac or indomethacin, at all the assessed hours, the pain measured was considerably less than in the suppository-free group (p < 0.05). Comparing the diclofenac and indomethacin groups, there were only significant differences in the 4 and 12 hour measurements: the diclofenac was more effective than the indomethacin (4th hour), but due to a shorter half-life, the diclofenac group in the 12th hour had more pain (p < 0.05). Diclofenac suppository is recommended at 4-hour intervals for all patients, without internal disorders, to decrease episiotomy pain.

Human breast milk and xenoestrogen exposure: a possible impact on human health

Human milk is the best natural and optimal food for neonates with several immunologic, developmental and practical advantages throughout childhood. Although the World Health Organization strongly supports breastfeeding, it recognizes the potential health risks posed by the presence of environmental toxicants in breast milk. Contamination of human milk is widespread and due to decades of inadequately controlled pollution by toxicants, persistent pesticides or chemical solvents. These chemicals tend to degrade slowly in the environment, to bioaccumulate in the food chain and to have long half-lives in humans. Many of these environmental pollutants have estrogen-like activities and, thus they are called environmental estrogen disruptors or xenoestrogens. Certain adverse health and reproductive outcomes are attributed to these chemicals in laboratory animals and in wildlife as well as in humans. Here, we review available data from breast milk monitoring studies suggesting the environmental chemicals that may affect child health through breastfeeding.

Antibiotics and breast-feeding: a critical review of the literature

Continuous breast-feeding, an integral component of the postpartum period, is often threatened upon maternal initiation of antibiotics. The real risk of antibiotic use while breast-feeding must be carefully analysed with regard to all the variables that influence the extent of antibiotic distribution into breast milk, including breast milk composition, physicochemical properties of the antibiotic (molecular weight, lipid solubility, pH, protein binding), length of feeding, and maternal disposition. In addition, infant disposition, including ability to absorb, metabolize, eliminate, and tolerate any amounts of antibiotic, must also be considered prior to maternal administration of antibiotic. The milk to plasma (M/P) ratio is a frequently quoted parameter used to predict drug distribution into breast milk. However, its utility is questionable and often fraught with misinterpretation. An alternative approach when the amount of antibiotic concentration in breast milk is known (through clinical trials) is to calculate an estimated or expected infant drug exposure factoring in known/expected milk consumption, drug concentration and bioavailability. In this review, the following antibiotic classes and current literature regarding their distribution into breast milk are critically reviewed: beta-lactam antibiotics, fluoroquinolones, sulfonamides, macrolides, aminoglycosides, tetracyclines, nitrofurantoin, metronidazole, vancomycin, clindamycin and chloramphenicol. In the majority of instances, these antibiotics do not distribute into breast milk in sufficient concentrations to be of any clinical consequence in the breast-feeding infant.

Models and methods for predicting drug transfer into human milk

Adverse effects in infants due to the ingestion of drugs and other xenobiotics remain an area of concern. A key parameter in assessing infant exposure via breast milk, the milk to plasma concentration ratio (M/P), has not been determined in vivo in humans for most drugs. There are various methods for predicting M/P, which involve in vitro experiments in mammary cell monolayers, assessment of drug binding to plasma and milk protein and lipid, in vivo experiments in animals, and regression models based on a compound's physicochemical characteristics. This article reviews these approaches in terms of their utility, advantages and disadvantages. Some combination of these methods is necessary for reasonably accurate prediction of M/P in humans.

Analytic considerations for measuring environmental chemicals in breast milk

The presence of environmental chemicals in human breast milk is of general concern because of the potential health consequence of these chemicals to the breast-fed infant and the mother. In addition to the mother's exposure, several features determine the presence of environmental chemicals in breast milk and their ability to be determined analytically. These include maternal factors and properties of the environmental chemical--both physical and chemical--such as its lipid solubility, degree of ionization, and molecular weight. Environmental chemicals with high lipid solubility are likely to be found in breast milk; they include polyhalogenated compounds such as polychlorinated biphenyls, polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, organochlorine insecticides, and polybrominated diphenylethers. These fat-soluble chemicals are incorporated into the milk as it is synthesized, and they must be measured in accordance with the fat content of the milk to allow for meaningful comparisons within an individual and among populations. Although the analytic approach selected to measure the environmental chemical is predominantly determined by the characteristics of the chemical, the concentration of the chemical in the milk sample and the existence of structurally similar chemicals (e.g., congeners) must be considered as well. In general, the analytic approach for measuring environmental chemicals in breast milk is similar to the approach for measuring the same chemicals in other matrices, except special considerations must be given for the relatively high fat content of milk. The continued efforts of environmental scientists to measure environmental chemicals in breast milk is important for defining the true contribution of these chemicals to public health, especially to the health of the newborn. Work is needed for identifying and quantifying additional environmental chemicals in breast milk from the general population and for developing analytic methods that have increased sensitivity and the ability to speciate various chemicals.

Xenobiotics and breastfeeding

Breastfeeding provides important benefits to mothers and infants and should be encouraged strongly as the optimal feeding choice for most infants. In assessing the effects of maternal medication on breastfeeding, clinicians must weigh the many benefits of breastfeeding for mothers and infants against the risk for exposing infants to a drug as it is present in breast milk. With regard to most medications, continued breastfeeding despite drug exposure is advantageous to mothers and infants.

Methods to identify and characterize developmental neurotoxicity for human health risk assessment. III: pharmacokinetic and pharmacodynamic considerations

We review pharmacokinetic and pharmacodynamic factors that should be considered in the design and interpretation of developmental neurotoxicity studies. Toxicologic effects on the developing nervous system depend on the delivered dose, exposure duration, and developmental stage at which exposure occurred. Several pharmacokinetic processes (absorption, distribution, metabolism, and excretion) govern chemical disposition within the dam and the nervous system of the offspring. In addition, unique physical features such as the presence or absence of a placental barrier and the gradual development of the blood--brain barrier influence chemical disposition and thus modulate developmental neurotoxicity. Neonatal exposure may depend on maternal pharmacokinetic processes and transfer of the xenobiotic through the milk, although direct exposure may occur through other routes (e.g., inhalation). Measurement of the xenobiotic in milk and evaluation of biomarkers of exposure or effect following exposure can confirm or characterize neonatal exposure. Physiologically based pharmacokinetic and pharmacodynamic models that incorporate these and other determinants can estimate tissue dose and biologic response following in utero or neonatal exposure. These models can characterize dose--response relationships and improve extrapolation of results from animal studies to humans. In addition, pharmacologic data allow an experimenter to determine whether exposure to the test chemical is adequate, whether exposure occurs during critical periods of nervous system development, whether route and duration of exposure are appropriate, and whether developmental neurotoxicity can be differentiated from direct actions of the xenobiotic.

Excretion of psychoactive drugs into breast milk. Pharmacokinetic principles and recommendations

The postpartum period is a time of great physical and emotional changes. The incidence of psychiatric illness is higher in this period than at any other time in a women's life. Therefore, the question of whether women receiving psychotropic drugs should continue breast feeding is an important one. Drug excretion in breast milk depends mostly on passive diffusion of the unionised unbound drug. Passive diffusion is affected mainly by the drug disposition in lactating mothers, by the physicochemical properties of the molecule and by the protein and lipid contents of breast milk. Indeed, breast milk can be considered as a compartment with bidirectional transfer rather than a reservoir into which drug accumulates. Benzodiazepines are the most prescribed psychotropic drugs. Generally there does not seem to be any contraindication to breast feeding after a single dose, provided the dose administered is relatively low. If higher doses are to be used or long term administration is required, then breast feeding should probably be discontinued, particularly with drugs with a long elimination half-life. On the basis of the average concentration of phenobarbital (phenobarbitone) in milk, breast feeding is not recommended. For glutethimide, breast feeding would appear to be safe for the infant when a single dose is taken occasionally. Zopiclone may also be prescribed on a short term basis to breast feeding mothers. Due to limited available data or to the large amount transferred to milk, administration of phenothiazines and nonphenothiazine tricyclic, butyrophenone, and benzamide antipsychotics to breast feeding mothers cannot be recommended. Breast feeding is not always considered an absolute contraindication to lithium therapy, but the mother should watch for signs of toxicity in her baby. Whether clomipramine should be contraindicated during breast feeding depends on the concentration of active metabolites in breast milk, and this has not yet been determined. It is probably safe for mothers to breast feed while receiving amitriptyline, but before more conclusive recommendations are made more infants should be studied. The available data suggest that the amount of doxepin and its metabolite in breast milk is small. However, the metabolite of doxepin may accumulate in the infant with risk of sedation and respiratory depression: therefore, an alternative antidepressant should be selected for breast feeding mothers.(ABSTRACT TRUNCATED AT 400 WORDS)

Different profiles of induced cotton effects of human and bovine lactoferrin by cibacron blue F3GA binding

1. The properties of complex formation of lactoferrin with Cibacron Blue F3GA dye have been studied by circular dichroic spectral analyses. The Cotton effects were induced by the interaction of lactoferrin with the dye and occurred in the wavelength range from 300 to 450 nm. 2. The patterns of changes in circular dichroic spectra of lactoferrin induced by the dye were different in bovine and human lactoferrin. 3. Iron ions bound to lactoferrin affected the profiles of induced Cotton effects in human lactoferrin but not in bovine lactoferrin. 4. While the dye bound co-operatively to human apo-lactoferrin, such co-operativeness was not observed in iron-saturated human lactoferrin.

Binding of drugs in milk: the role of casein in milk protein binding

Unbound fractions of 14C-labeled diazepam and tenoxicam in skimmed milk of various species (man, horse, goat, cow, sheep, dog, rabbit) with different milk compositions were determined. Furthermore, the protein binding of five 14C-labeled benzodiazepines differing in their lipophilicity (bromazepam, clonazepam, diazepam, flumazenil, and flunitrazepam) were measured in human milk and in artificially prepared solutions of individual milk proteins (lactoferrin, 2.4 g/liter; alpha-lactalbumin, 2.1 g/liter; albumin, 0.4 g/liter; and casein--2.1, 3.4, and 13.3 g/liter). The extent of binding was determined by equilibrium dialysis of protein solution against 1/15 M phosphate buffer, made isocryoscopic with lactose. The results showed that the casein fraction is a major binding component in milk for all tested drugs. The extent of binding of diazepam and tenoxicam in the milk of various species was independent of the whey protein concentration. In human milk the fraction of bromazepam, clonazepam, diazepam, and flunitrazepam bound to casein was higher than that bound to any other of the milk proteins tested. Albumin contributed little to the overall binding of these benzodiazepines, and lactoferrin and alpha-lactalbumin did not account for significant binding. The benzodiazepine antagonist flumazenil showed the lowest overall binding in milk and in casein solution. As the casein concentration is highest in colostral milk and drops during the course of lactation, it is expected that M/P ratios of drugs strongly bound to casein are higher during the first days postpartum than in later phases of lactation.