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All glaucoma patients who need treatment with drops, need to consider, with their ophthalmologist, the possible benefits and potential side effects of any medication. When glaucoma affects a woman who is pregnant, breast-feeding, or considering having a baby, there are additional considerations in the strategies needed for safe treatment. Now there are two patients involved - the mother and the baby - and the ways in which a baby’s tissues and organs react to drugs may be quite different from those in adults.
As we are all aware, drugs can have harmful effects on the development of a baby’s organ systems. The earlier in pregnancy the drugs are used, the more frequent and more severe the problems can be. But even later in pregnancy, or after birth if the infant is being breast-fed, drugs can have unwanted effects.
When eye drops are instilled, some is absorbed into the general circulation, and travels all over the body. It can pass through the placenta and reach high concentrations in the baby’s blood too. If a baby is being breast-fed, it can pass into the milk, and thus get into the baby’s circulation as well.
Because glaucoma is relatively uncommon in women of child-bearing age, this is a problem which is not encountered too often, fortunately. When it does occur, it can be very challenging indeed. This is particularly so as there have been very few studies in humans on the effects of anti-glaucoma drugs on infant health - for obvious reasons.
By using special techniques when instilling eye drops - such as the double dot ("don’t open the eyes" and "digital occlusion of the tear duct") - the amount of medication which is absorbed into the blood can be reduced by up to two-thirds. While this is significant in reducing general side effects, it cannot be relied upon to protect an unborn or newly born child. Neither can the good advice to use any medication at the lowest possible concentration and as infrequently through the day as possible.
During normal pregnancy the eye pressure tends to drop. While this may make treatment less necessary, it is only a partial effect, and may not be enough to protect the pregnant woman from further optic nerve damage during the pregnancy. Argon laser trabeculoplasty and/or surgery may be required to lower eye pressure to safe levels so that eye drops are no longer needed. The laser can be performed with little if any additional medications, but surgery requires a variety of drugs to make it safer and more likely to succeed. It is therefore highly desirable that any young woman planning to have a family who is using regular anti-glaucoma medications (or any other drugs) discusses this with her doctor in advance, so that appropriate planning can take place.
Some comments on specific agents:
Beta-blockers (timolol, levo-bunolol, betaxolol)
Officially it is recommended that these agents be avoided in early pregnancy. In later stages, and during breast-feeding, they can cross into the baby and cause depression, slow heart rates and lower blood sugar levels. They may also interfere with contractions of the womb, and thus affect the birth.
Miotics (pilocarpine, carbachol, ecothiopate iodide)
Although animal investigations suggested a harmful effect on unborn babies, a large study of pilocarpine found no association with birth defects when used in the first four months of pregnancy. In the newborn, however, it can cause weakness, fits and high temperatures. The other agents in this group have been shown to contribute to defects in animals, and to cause a muscle weakness in babies.
Adrenergic compounds (adrenaline, dipivefrin)
With adrenaline, early use in pregnancy has been described as contributing to cataracts and hernias. Although dipivefrin leads to much lower blood levels of adrenaline than if adrenaline itself is used as eye drops, it should be used with extreme caution, if at all, in pregnancy and with breast-feeding. Apraclonidine has no harmful effects on pregnant rabbits and rats, but there have been no human studies. Brimonidine does cross the placenta, but may not be in milk. If it does reach the baby, it can cause marked lowering of blood pressure, and may be associated with increased miscarriages.
Carbonic anhydrase inhibitors (acetazolamide, methazolamide, dorzolamide)
The first two of these agents (which are taken as tablets) are known to cause defects in babies, and should be avoided entirely. Dorzolamide (which is used as a drop) may not be pumped into the milk, and thus may be more safe - however, there have been no human studies performed.
Prostaglandin derivatives (latanoprost)
Safety in human pregnancy and breast-feeding has not been established, but experiments in rabbits and rats have shown no malformations even at high doses. It does cross into human milk, however. There is a theoretical possibility that using prostaglandins may induce premature labour - but this is unlikely as latanoprost is not one of the prostaglandins most liable to do this.
Even if the answers are not, the messages are clear:
- try to avoid ALL medications during pregnancy and breast-feeding if at all possible;
- find other means of lowering eye pressure during this time if it is necessary;
- plan ahead - if pregnancy is desired, take the time to control the glaucoma by laser or by surgery first, and then conceive;
- if drugs HAVE to be used, use the least number, the lowest concentration the least number of times each day, and employ the special techniques available to minimise drug concentrations in the blood.
