Is there any difference between the placental passage of betamethasone and prednisolone, and is gro

Fråga: Is there any difference between the placental passage of betamethasone and prednisolone, and is growth retardation a dose-dependent effect? Background: This question is regarding a woman in her 17th week of pregnancy with her second child. During her first pregnancy she was prescribed prednisolone for her severe asthma. The child was delivered by cesarean section in the 31st week, to avoid fetal growth retardation. For her second pregnancy she is being prescribed 10 mg of betamethasone (Betapred) daily and 8 mg IV per week via a porta cath. The patients is concurrently taking numerous other medications for her asthma including: fluticasone, theophylline, salmeterol, bambuterol, salbutamol, budesonide, phenylpropanolamine, and aminophylline. The physician would like to change her betamethasone to prednisolone because he believes it will have less effect on the fetus, and wishes to know if this is true.

Sammanfattning: There is currently no data available which compares the amount of placental passage of betamethasone and prednisolone, nor is there any information pertaining to a corticosteroid dose relationship and growth retardation of the fetus.

Svar: As a group, the corticosteroids all cross the placenta (1-4). It is interesting to note however, that no data could be found which compared how much of each drug will cross the placenta.

What is known of these specific agents is that 47 percent of the betamethasone dose is metabolized by the placenta to its inactive form (1). Prednisolone is also metabolized by the placenta, in similar amounts, to inactive prednisone or less active cortisone (1). Prednisone, is hepatically metabolized into prednisolone (3).

Analysis of the structure-activity-relationship (SAR) of the two agents shows that, according to their structures, they should both cross the placenta in equal ratios (5). However, these agents are not equipotent. For instance, 5 mg of prednisolone is equal to 0.75 mg of betamethasone. So, with this patient in mind, her 10 mg of betamethasone is equal to 67 mg orally of prednisolone/day, while for the IV form, 8 mg of betamethasone/week is equal to an additional 53 mg IV/week (3).

As for side effects suffered by the fetus, such as growth retardation, no data could be found giving a dose-dependent or non-dependent relationship, only that hypoadrenalism can occur (2). There are reports of fetal hypoglycemia from the use of betamethasone, but there were no congenital defects reported, and use in asthmatic mothers does not increase the risk of fetal morbidity. As for prednisolone, studies show little, if any effect on the developing fetus (1, 4). There is one case report of a fetus being born with cataracts after intrauterine exposure to prednisolone (4).