GLAUCOMA MANAGEMENT DURING PREGNANCY

GLAUCOMA MANAGEMENT DURING PREGNANCY

GUEST AUTHOR

SAMEERA SHAMSHAD

Ajmal Khan Tibbiya College,

Aligarh, India.

A. Medical therapy

Appropriate management of pregnant women with glaucoma requires a balance between the treatment's risk to the fetus, as well as the mother.

80% of the volume in a typical eye drop drains through the nasolacrimal duct and is then absorbed systemically.

Treating any pregnant woman with topical antiglaucoma medications carries the risk of exposure of the unborn child due to systemic absorption. Once the drug passes through the placenta and enters the fetal circulation, it may be excreted into the amniotic fluid from the kidneys, lungs or skin.

The US Food and Drug Administration (FDA) classification of drug risk in pregnancy is displayed below.

No topical ophthalmic drugs are placed in category A or X. Most topical glaucoma medications are labeled in pregnancy Category C. The only drugs in category B are Brimonidine and Dipivefrin.

Food and Drug Administration Drug Risk categories in pregnancy:

Category A= These drugs are the safest for pregnant patients. There is no increased risk of fetal abnormalities found on studies in pregnant women.

Category B= There is evidence of adverse effects on the fetus in animal studies in pregnant women, but studies in pregnant women have failed to demonstrate fetal risk.

Category C= Animal studies have shown evidence of harm to the fetus and there are no adequate or well-controlled studies in pregnant women.

Category D= Risk to the fetus has been demonstrated in well-controlled or observation studies in pregnant patients. However, the benefits of therapy may outweigh the potential risk.

Category X= Evidence the fetal abnormalities in well controlled studies in animals or pregnant patients. The drug is contraindicated in pregnancy.

1. PRESERVATIVE USED IN ANTIGLAUCOMA DRUGS:

The most common preservative in antiglaucoma glaucoma drugs is benzylkonium chloride (BAK). BAK has not been found to be associated with any discernible visceral malformations, although minor sternal defects occurred in fetuses exposed to a single dose of 100-200 mg/kg BW. The concentration of BAK in antiglaucoma eyedrops varies from 0.01% to 0.05%.

2. BETA BLOCKERS:

The nonselective topical betablockers are timolol maleate, timolol hemihydrates, carteolol, levobunolol and metipranolol.

Betablockers are class C medications.

Systemic betablockers are used for management of hypertension during pregnancy. Thus, some suggest the use of topical betablockers as safe and justified. However, their use near term (2nd-3rd trimester according to others) may result in fetal and neonatal bradycardia, arrhythmia, hypotension and hypoglycaemia. Respiratory distress and apnoea have also been reported following in utero exposure.

Neurologic complications, specifically lethargy and confusion, have also been reported with betablocker use during pregnancy. There is also risk of teratogenicity with the use of betablockers especially during the first trimester.

The data on the safety of discontinuing treatment 24-48h before delivery are conflicting. When reported, neonatal symptoms due to β-blockade are usually mild and resolve within 48h.

3. CARBONIC ANHYDRASE INHIBITORS=

(a) Oral carbonic anhydrase inhibitors (CAIs): Acetazolamide and methazolamide are oral CAIs used for glaucoma management. These agents are category C for use during pregnancy.

 Many studies suggest that Acetazolamide should be avoided during pregnancy, especially in the first trimester due to potential metabolic complications to the newborn or breast-feeding child. Systemic high dose carbonic anhydrase inhibitors in rats can result in forelimb anomalies which may suggest that this medication is teratogenic. A single case of sacrococcygeal teratoma, a rare condition in an infant born to a mother treated with Acetazolamide until the 19th week of pregnancy is reported.

(b) Topical carbonic anhydrase inhibitors: Dorzolamide and Brinzolamide= These medications are classified as Category C medications.

There are no studies showing any side-effects to the fetus or breast-feeding newborns, therefore, these agents might be used if the advantages for the mother outweigh the risks to the baby.

4. PROSTAGLANDIN ANALOGUES=

Bimatoprost, latanoprost and travoprost are Prostaglandin-F2 analogues, commonly used in patients with glaucoma.

Prostaglandins increase uterine tone and can cause reduced perfusion to the fetus. Prostaglandins, being oxytocic and luteolytic, can increase uterine tone and stimulate uterine contractions producing premature labor.

There are no reports of premature labor associated with the use of these drugs for glaucoma, and if there are compelling treatment indications as in the case of severe glaucoma, they may be considered for use. Given the theoretical risk of premature delivery, prostaglandin analogues are not a choice for first-line medication in pregnancy. 

While some pharmacologists uphold that latanoprost and travoprost have insufficient active ingredients to cause adverse effects on the foetus, others believe that the use of prostaglandins is generally contra-indicated in pregnant women.

Latanoprost; Travoprost and Bimatoprost are Category C medications.

5. PARASYMPATHOMIMETICS:

Parasympathomimetics are classified as Category C.

Pilocarpine and carbachol have demonstrated teratogenic and adverse effects in animals.

On the contrary, a large collaborative study found no association between their use during the first 4 months of gestation and occurrence of congenital abnormalities.

6. SYMPATHOMIMETICS:

(A) Non-selective sympathomimetics= Epinephrine and Dipivefrin are rarely used to treat glaucoma.

Although these drugs are Category B, there is a high prevalence of systemic and local side effects such as tachycardia, arrythmia, hypertension, headaches, red eyes, adrenochrome deposits and frequent allergies.

(B) Alpha agonists= The alpha selective agonists available commercially include clonodine, apraclonidine and Brimonidine. The latter is classified as a Category B medication. Even if brimonidine is used during pregnancy, it should be discontinued before labor and during breastfeeding to prevent potential fetal apnea

The systemic hypotension and sedative side-effects of clonodine have limited its use as an antiglaucoma agent.

7. FIXED COMBINATION ANTIGLAUCOMA DRUGS:

The available fixed combinations include timolol-dorzolamide, timolol-brinzolamide, timolol-brimonidine, timolol-xalatan, timolol-bimatoprost and timolol-travoprost.

All drugs are Category C.

B. SURGICAL MANAGEMENT OF GLAUCOMA IN PREGNANCY:

1. Anesthesia in Pregnancy= When using anesthesia for pregnant patients, it is important to use the minimal effective dosage and avoid unnecessary medications.

Most local anesthetics have not been shown to be teratogenic in humans (etidocaine, prilocaine, lidocaine are class B medications).

Bupivicaine and Mepivicaine use may lead to fetal bradycardia according to data in animal studies and are Category C medications.

2. Laser trabeculoplasty= In laser trabeculoplasty, laser energy is directed locally at the trabecular meshwork of the eye with no known systemic effects. There are multiple reports of laser trabeculoplasty in pregnant patients without any complications and with successful lowering of IOP.

3. Cyclophotocoagulation= It directs laser energy to destroy cells of the ciliary body and thus, decrease aqueous production.

One report found cyclophotocoagulation to be effective in lowering of IOP without complications in this group of patients.

4. Tube shunt surgery: It can be performed in pregnant patients, having uncontrolled IOPs.

5. Trabeculectomy: Antimetabolites such as Mitomycin-C and 5-Flurouracil should be avoided in pregnancy because of their teratogenic potential.

Trabeculectomy with retrobulbar anesthesia patients have demonstrated good IOP control with no complications.

Although glaucoma surgery is usually a short procedure, the length and complexity of the procedure as well as patient positioning should be considered when evaluating a pregnant patient for surgery.

There is increased risk during pregnancy of thromboembolic disease and pregnant patients undergoing longer procedures may benefit from graduated compression stockings or pneumatic compression devices. Placing the pregnant patient on her left side may help prevent the gravid uterus from causing aortocaval compression during long surgical procedures.