The effect of ephedrine (nine patients) and theophylline (seven patients) on dexamethasone metabolism was studied before and after three weeks of drug therapy in 16 asthmatics. Five patients were studied similarily but treated with placebo. After treatment with ephedrine, there was a mean decrease in plasma dexamethasone half-life (t1/2) of 132 minutes, or 36 per cent (P less than 0.025), and mean increase in metabolic clearance rate (MCR) of 148 liters/day, or 42 per cent (P less than 0.001). Increase in the excretion of urinary radioactivity, predominantly in the conjugated fractions, was noted. In contrast, theophylline and placebo therapy resulted in no significant changes in dexamethasone t1/2 or MCR. The rate of urinary excretion of radioactivity was reduced after theophylline treatment. Since ephedrine accelerates labeled dexamethasone clearance while theophylline does not, caution is necessary when prescribing ephedrine for asthmatics requiring long-term therapy with dexamethasone and probably other corticosteroids. It would appear from the present investigation that theophylline is a more appropriate bronchodilator for these patients.

Adult↗

PubMedDate not supplied

Lead, zinc, and erythrocyte delta-aminolevulinic acid dehydratase: relationships in lead toxicity.

A lead-intoxicated patient with extremely high blood lead levels and unexpectedly mild symptoms was studied prior to and following treatment with calcium disodium edetate (ethylenediaminetetraacetic acid) and then prior to and following oral administration of zinc sulfate. During chelation therapy, erythrocyte (delta)-aminolevulinic acid dehydratase (ALAD) activity decreased as blood lead levels fell. Urinary excretion of zinc increased and was more than 3.5 times greater than that of lead. The ratio of blood lead to serum zinc was greatest (1.47) when ALAD activity was lowest. Oral administration of zinc sulfate following chelation therapy resulted in a significant increase in mean ALAD activity. In vitro additions of zinc chloride to the patient's erythrocytes resulted in reactivation of ALAD activity. These studies suggest that zinc is an important element in the ALAD system in man. Zinc may play a protective role in lead toxicity, and zinc supplementation may be a useful adjunct to chelation therapy for lead toxicity.

Adult↗

PubMedDate not supplied

The effects of protective equipment on styrene exposure in workers in the reinforced plastics industry.

This study was designed to determine whether styrene absorption through the skin results in measurable changes in biologic indicators of styrene exposure using a group of workers engaged in hand lay-up operations during which extensive styrene skin contact occurs. Serial measurements of expired breath and blood styrene and urinary excretion of mandelic and phenylglyoxylic acid were made in eight female workers during 4 consecutive days using different experimental conditions including either (1) gloves/protective clothing alone, (2) respirator alone, (3) both gloves/protective clothing and respirator, or (4) neither respirator nor gloves/protective clothing. A two-by-two factorial design imbedded in a Latin square design allowed estimation of the effects of the two types of protection (i.e., gloves/clothing and respiratory) and any interaction. Levels of styrene in venous blood and expired breath and urine mandelic and phenylglyoxylic acid excretion were no different when gloves/clothes were used as protection compared to no protection at all. Significant reduction in all biologic indices occurred when respiratory protection was used. The results of the study suggest that percutaneous absorption of styrene is not a significant exposure source and does not significantly contribute to the body burden of styrene of workers in the reinforced plastic industry engaged in hand lay-up operations. Respiratory protective devices were the most effective means for reducing styrene absorption. Even though skin absorption of styrene is limited, skin protection is necessary because of the risk of dermatitis.

Air Pollutants, Occupational↗