Excretion of gold into human breast milk

GOLD: human exposure and update on toxic risks

Gold is ubiquitous in the human environment and most people are in contact with it through wearing jewelry, dental devices, implants or therapies for rheumatoid arthritis. Gold is not a nutrient but people are exposed to it as a food colorant and in food chains. The present review discusses the hazards faced in personal and domestic use of gold and the far greater risks presented through occupational exposure to the metal in mining and processing gold ores. In the last situation, regular manual contact or inhalation of toxic or carcinogenic materials like mercury or arsenic, respectively, presents far greater hazard and greatly complicates the evaluation of gold toxicity. The uses and risks presented by new technology and use of nanoparticulate gold in anti-cancer therapies and diagnostic medicine forms a major consideration in gold toxicity, where tissue uptake and distribution are determined largely by particle size and surface characteristics. Many human problems arise through the ability of metallic gold to induce allergic contact hypersensitivity. While gold in jewelry can evoke allergic reactions, other metals such as nickel, chromium and copper present in white gold or alloys exhibit more serious clinical problems. It is concluded that toxic risks associated with gold are low in relation to the vast range of potential routes of exposure to the metal in everyday life.

Transfer of drugs and other chemicals into human milk

The American Academy of Pediatrics places emphasis on increasing breastfeeding in the United States. A common reason for the cessation of breastfeeding is the use of medication by the nursing mother and advice by her physician to stop nursing. Such advice may not be warranted. This statement is intended to supply the pediatrician, obstetrician, and family physician with data, if known, concerning the excretion of drugs into human milk. Most drugs likely to be prescribed to the nursing mother should have no effect on milk supply or on infant well-being. This information is important not only to protect nursing infants from untoward effects of maternal medication but also to allow effective pharmacologic treatment of breastfeeding mothers. Nicotine, psychotropic drugs, and silicone implants are 3 important topics reviewed in this statement.

Treatment with immunosuppressive and disease modifying drugs during pregnancy and lactation

Active rheumatic disease may necessitate the treatment of pregnant and lactating patients with disease modifying (DMARD) or immunosuppressive drugs. This review summarizes data from the literature, and attempts to give some recommendations. Possible teratogenic effects of gold, penicillamine, and chloroquine are still disputed. As long as the issue is not settled, it seems prudent to stop using these agents as soon as pregnancy is diagnosed. Hydroxychloroquine has been used by some rheumatologists for treating pregnant patients with systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA) without malformations detected in the neonates. Sulphasalazine does not increase the rate of congenital abnormalities. Selected case reports have not shown any teratogenicity of cyclosporine A so far. However, the drug may cause fetal retardation. The use of standard doses of azathioprine does not increase the risk of congenital anomalies. By contrast, the antitumor agents cyclophosphamide, chlorambucil, and methotrexate are possibly teratogenic when given during early pregnancy, but may be less harmful in late pregnancy. Data on the excretion of DMARD and the cytostatic drugs are sparse. Because of insufficient data, breast feeding is not recommended in patients on antimalarials, penicillamine, cyclosporine A, and cytostatic drugs. Intramuscular gold and sulphasalazine seem to impose no major risk on the nursing infant.

Use of sodium aurothiomalate during lactation

The report concerns a mother who breast fed her infant whilst receiving sodium aurothiomalate for the treatment of rheumatoid arthritis. The milk:serum concentration ratio was not constant, reflecting the non-concurrence of the concentration-time profiles of gold in milk and maternal serum after i.m. injection. Gold was detected in the infant's serum. Calculations indicate that the weight-adjusted dose to the infant exceeded that received by the mother.

Antirheumatic drugs in pregnancy and lactation

The natural inclination of patients with rheumatic diseases wishing to become pregnant or to breast feed will be to take as few medications as possible. The guidelines outlined above can be used to balance the risk of drug effect on the fetus or neonate with the risk of inducing a flare in disease activity by stopping the drug. Although there are situations where no information on drug behaviour during pregnancy or lactation exists, some guidelines can be developed from a knowledge of the drug's inherent metabolism. In the majority of the rheumatic diseases, disease activity can be reduced to a minimum using the smallest possible dose of drugs known to be safe in pregnancy and lactation, thus providing minimum risk to mother, fetus and neonate.

Drugs in human milk. Clinical pharmacokinetic considerations

Drugs ingested by a lactating mother would be expected to appear in human milk to some extent and be ingested by a breast-feeding infant. Drugs pass from maternal plasma into milk by passive diffusion and are distributed within the aqueous, protein and lipid phases of milk. Distribution into milk will be affected by physiochemical characteristics of the drug: acid-base characteristics, relative protein binding in plasma and milk, and lipid solubility, as well as milk composition. The milk-to-plasma concentration ratio is the most commonly quoted index of drug distribution into human milk. However, calculation of the daily infant dose of drug ingested in milk, and from this the dose in milk relative to the maternal dose on a weight-adjusted basis, is a more relevant indicator of infant exposure to a drug. This is particularly true for drugs with a high volume of distribution, for which only a small proportion of the mother's dose is contained within the plasma and available for distribution into milk. A better indication of infant exposure to a drug is the steady-state plasma drug concentration in a breast-feeding infant, the major determinants of which are the dose rate (via milk) and the oral availability and clearance in the infant. Although in neonates the rate of absorption may be different from adults, there is little evidence that its extent is significantly different. Clearance, however, is impaired in very young infants, particularly if premature. The decreased clearance would result in a proportional increase in steady-state plasma concentrations in the breast-feeding infant. Consideration of the dose ingested in milk and the approximate clearance in infants of different ages allows estimation of likely steady-state plasma concentrations in breast-feeding infants. From these considerations, recommendations regarding the safety of drugs during breast-feeding can be made. Drugs which are very toxic or have dose-independent toxicity should be considered separately. Recommendations regarding 'social' drugs such as nicotine, alcohol, caffeine and theobromine are particularly difficult, as doses are uncontrolled and vary variable.

Principles of drug biodisposition in the neonate. A critical evaluation of the pharmacokinetic-pharmacodynamic interface (Part I)

Rational pharmacotherapy is dependent upon an understanding of the clinical pharmacokinetic and pharmacodynamic properties of the drugs employed. Although the available data on drug biodisposition and action in the neonate have increased considerably in the last few years, pharmacokinetic-pharmacodynamic interactions for many drugs remain poorly understood. The ontogeny of drug absorption, distribution, metabolism, and elimination are addressed in this review. Drug absorption from any site depends upon both the physicochemical properties of the drug and a variety of patient factors. Absorption of orally administered drugs may be affected by changes in gastric acidity and emptying time as well as by bile salt pool size, bacterial colonisation, and extraintestinal disease states such as congestive heart failure. Factors affecting drug absorption following intramuscular, percutaneous, and rectal administration are also discussed. Drug distribution in the neonate is influenced by a variety of important and predictable age-dependent factors. The developmental aspects of protein binding and body water compartments are described. Additionally, hepatic drug metabolism assumes an important role in understanding the pharmacokinetic and pharmacodynamic properties of many compounds. Certain biotransformation pathways, including hydroxylation by the P450 mono-oxygenase system and glucuronidation, demonstrate only limited activity at birth, while other pathways, such as sulphate or glycine conjugation, appear very efficient at birth. Elimination of drugs excreted unchanged in the urine is dramatically reduced in the newborn, compared with older infants and children, due to immaturity of both glomerular filtration and tubular secretory processes. The glomerular filtration rate remains markedly reduced prior to 34 weeks gestational age, increasing as a function of post-conceptual age until adult values are achieved by approximately 2.5 to 5 months of age. Tubular secretory capacity is also limited at birth, approaching adult values by approximately 7 months of age. Published reports describing the pharmacokinetics and pharmacodynamics of commonly used drugs in the neonatal period, as well as differences in drug biodisposition among premature infants, full term neonates, and older infants and children, are reviewed. Our recommendations for neonatal drug therapy are based upon a critical interpretation of these data, an understanding of fetal development and maturational processes, and an understanding of how disease states may affect drug biodisposition in the neonate.