Management of glaucoma in pregnancy and lactation

A 30-year-old pregnant woman with glaucoma is presented. The management of her case is used as a basis for a discussion of the use of glaucoma medications, including newer formulations, during pregnancy and lactation.

QSAR analysis of drug excretion into human breast milk

Breast feeding has increased by approximately 25% in the United States during the past decade and this trend appears to be continuing. The number of drugs available to lactating women is also growing at a rapid pace. The excretion of drugs into breast-milk presents a potential danger to infants. In spite of this, little is known about the excretion of drugs into breast-milk. The ability to predict which drugs are potential hazards would be very useful in the clinical setting. This study quantitatively correlates the human milk to plasma concentration ratio of various basic and acidic drugs (log M/P) with the square root of the molecular weight, the partition coefficient (log P) and the degree of dissociation (log U/D). For basic drugs there is a negative-dependence on both log P and log U/D. High lipophilicity favours protein binding and reduces the amount of drug available for diffusion into milk. Therefore, as log P increases, the log M/P decreases. The negative-dependence on log U/D indicates that the higher the degree of dissociation of the base in plasma, the greater the log M/P will be. This fits well with the concept of ion-trapping. A strong base is more likely to be transferred and then trapped in milk which has a lower pH than plasma. For acidic drugs there is a negative-dependence on both square root (MW) and log P. The negative-dependence on square root (MW) suggests that large molecules are less likely to be able to diffuse into the milk. A negative-dependence on log P appears to hold true for bases and acids. Log M/P decreases as log P increases. This is probably due to increased protein binding by lipophilic drugs through non-specific hydrophobic interaction with plasma protein.

Management of hypertension during lactation

There has been a dramatic increase in the number of women breast-feeding during the last decade. Since little is known about the excretion of antihypertensive drugs into human breast milk, the management of hypertension during lactation can be problematical. To enable the clinician to better advise the hypertensive, lactating mother, the published literature on the excretion of antihypertensive agents into human milk has been reviewed and is presented in this report.

Penetration of some antibiotics into the lacrimal fluid of sheep

Antibiotic concentrations were determined in the lacrimal fluid of sheep following subcutaneous application of penicillin/dihydrostreptomycin into the lower eyelid, and intramuscular administration of spiramycin base, tiamulin, and oxytetracycline formulations. The penetration of penicillin and dihydrostreptomycin into the lacrimal fluid was poor. The spiramycin and tiamulin concentrations in the lacrimal fluid were 10- and 4-fold higher than in the serum. The peak spiramycin concentration in the lacrimal fluid was 3.4 +/- 0.8 microgram/ml at 8 h post injection (p.i.) and the drug could be detected at least 72 h p.i. For tiamulin and oxytetracycline (OTC) peak concentrations of 1.53 +/- 0.70 and 1.88 +/- 1.9 micrograms/ml, respectively, were achieved in the lacrimal fluid and these drugs could be detected 25 to 30 h p.i. The OTC and tiamulin concentration-time curves for lacrimal fluid and serum were parallel, whereas for the spiramycin appearance in the lacrimal fluid was delayed.

Effects of different buffer species on partition coefficients of drugs used in quantitative structure-activity relationships

A study was conducted in which the same organic solvent, 1-octanol, and different buffer systems were used to obtain intercorrelations among log Pcorr values given by log P (octanol-water) = a log P (octanol-buffer) + b, where a and b are different constants for the different systems used. The range of a was 0.418-1.156 and that of b was -1.962-1.176 for the four buffer systems examined. Only with neutral drugs was the slope (a) close to 1.0 and the intercept (b) close to 0.0 for the three buffer systems studied. For acidic drugs, only 1-octanol-phosphate buffer gave a 1:1 correlation with 1-octanol-water partition coefficients. Acetate and bicarbonate buffer systems gave different correlations. For basic drugs, none of the three systems examined gave a 1:1 correlation with 1-octanol-water partition coefficients.