Bartter syndrome (BS) is a rare inherited disease characterised by a defect in the thick ascending limb of the loop of Henle, which results in low potassium levels (hypokalemia), increased blood pH (alkalosis), and normal to low blood pressure. There are two types of Bartter syndrome: neonatal and classic. A closely associated disorder, Gitelman syndrome, is milder than both subtypes of Bartter syndrome. Signs and symptoms
In 90% of cases, neonatal Bartter syndrome is seen between 24 and 30 weeks of gestation with excess amniotic fluid (polyhydramnios). After birth, the infant is seen to urinate and drink excessively (polyuria, and polydipsia, respectively). Life-threatening dehydration may result if the infant does not receive adequate fluids. About 85% of infants dispose of excess amounts of calcium in the urine (hypercalciuria) and kidneys (nephrocalcinosis), which may lead to kidney stones. In rare occasions, the infant may progress to kidney failure.Patients with classic Bartter syndrome may have symptoms in the first two years of life, but they are usually diagnosed at school age or later. Like infants with the neonatal subtype, patients with classic Bartter syndrome also have polyuria, polydipsia, and a tendency to dehydration, but normal or just slightly increased urinary calcium excretion without the tendency to develop kidney stones. These patients also have vomiting and growth retardation. Kidney function is also normal if the disease is treated, but occasionally patients proceed to end-stage kidney failure. Bartter syndrome consists of low levels of potassium in the blood, alkalosis, normal to low blood pressures, and elevated plasma renin and aldosterone.
There is some evidence to support its effectiveness in reducing seizure frequency when used as an add-on therapy for drug-resistant focal epilepsy but there are concerns over tolerability. Pregnancy
There is limited data analyzing the impact of oxcarbazepine on a human fetus. Animal studies have shown increased fetal abnormalities in pregnant rats and rabbits exposed to oxcarbazepine during pregnancy. In addition, oxcarbazepine is structurally similar to carbamazepine, which is considered to be teratogenic in humans (pregnancy category D). Oxcarbazepine should only be used during pregnancy if the benefits justify the risks.Pregnant women on oxcarbazepine should be closely monitored, as plasma levels of the active metabolite licarbazepine have been shown to potentially decrease during pregnancy. Breastfeeding
Oxcarbazepine and its metabolite licarbazepine are both present in human breast milk and thus, some of the active drug can be transferred to a nursing infant. When considering whether to continue this medication in nursing mothers, the impact of the drugs side effect profile on the infant, should be weighed against its anti-epileptic benefit for the mother. Side effects
Side effects are dose-dependent. The most common include dizziness, blurred or double vision, nystagmus, ataxia, fatigue, headaches, nausea, vomiting, sleepiness, difficulty in concentration and mental sluggishness.Other rare side effects of oxcarbazepine include severe low blood sodium (hyponatremia), anaphylaxis / angioedema, hypersensitivity (especially if experienced with carbamazepine), toxic epidermal necrolysis, Stevens–Johnson syndrome, and thoughts of suicide.Measurement of serum sodium levels should be considered in maintenance treatment or if symptoms of hyponatremia develop.