Ketanserin for the treatment of preeclampsia

The 5-HT2 antagonist ketanserin is an open channel blocker of human cardiac ether-à-go-go-related gene (hERG) potassium channels

BACKGROUND AND PURPOSE

Ketanserin, a selective 5-HT receptor antagonist, prolongs the QT interval of ECG in patients. The purpose of the present study was to determine whether ketanserin would block human cardiac ether-à-go-go-related gene (hERG) potassium channels.

EXPERIMENTAL APPROACH

Whole-cell patch voltage-clamp technique was used to record membrane currents in HEK 293 cells expressing wild type or mutant hERG channel genes.

KEY RESULTS

Ketanserin blocked hERG current (I(hERG)) in a concentration-dependent manner (IC50=0.11 microM). The drug showed an open channel blocking property, the block increasing significantly at depolarizing voltages between +10 to +60 mV. Voltage-dependence for inactivation of hERG channels was negatively shifted by 0.3 microM ketanserin. A 2.8 fold attenuation of inhibition by elevation of external K+ concentration (from 5.0 to 20 mM) was observed, whereas the inactivation-deficient mutants S620T and S631A had the IC50s of 0.84 +/- 0.2 and 1.7 +/-0.4 microM (7.6 and 15.4 fold attenuation of block). In addition, the hERG mutants in pore helix and S6 also significantly reduced the channel block (2-59 fold) by ketanserin.

CONCLUSIONS AND IMPLICATIONS

These results suggest that ketanserin binds to and blocks the open hERG channels in the pore helix and the S6 domain; channel inactivation is also involved in the blockade of hERG channels. Blockade of hERG channels most likely contributes to the prolongation of QT intervals in ECG observed clinically at therapeutic concentrations of ketanserin.

Functional reactivity of 5-HT receptors in human umbilical cord and maternal subcutaneous fat arteries after normotensive or pre-eclamptic pregnancy

OBJECTIVE

To investigate the functional reactivity of 5-hydroxytryptamine (serotonin; 5-HT) receptors in foetal umbilical cord arteries (UCA) and maternal subcutaneous fat resistance arteries (SFA) in normotensive and pre-eclamptic pregnancy.

DESIGN

Study groups were divided based on the presence or absence of pre-eclampsia and the duration of gestation.

METHODS

Segments of UCA and SFA were mounted in tissue baths and concentration-response curves to 5-HT and sumatriptan (5-HT1B/1D receptor agonist) were constructed in the absence or presence of ketanserin (5-HT2A receptor antagonist) or GR125743 (5-HT1B/1D receptor antagonist).

RESULTS

Both 5-HT and sumatriptan contracted all UCA segments studied. The responses to 5-HT and the potency of ketanserin in UCA were not different between the study groups, indicating a similar profile of the 5-HT2A receptor. In contrast, the potencies of sumatriptan and GR125743 were significantly higher in normotensive full-term pregnancies than in normotensive pre-term pregnancies in UCA. The response to sumatriptan in UCA arteries was not significantly different between pre-eclamptic and normotensive pregnancies. However, the potency of both sumatriptan and GR125743 was positively correlated to the gestational age in the normotensive group, whereas this relationship was absent in the pre-eclamptic group. In SFA, responses to 5-HT and sumatriptan were not different between the pre-eclamptic patients and normotensive controls.

CONCLUSIONS

In both UCA and SFA, 5-HT1B/1D and 5-HT2A receptors mediate vasoconstriction. The sensitivity of 5-HT1B/1D receptors increases in the last trimester in the UCA in normal pregnancies, which seems to be expedited in pre-eclamptic patients. Further studies on 5-HT1B/ID receptors will thus give new insights into the foetal development and pathophysiology of pre-eclampsia.

Insufficient efficacy of intravenous ketanserin in severe early-onset pre-eclampsia

OBJECTIVE

To analyze the efficacy of intravenous ketanserin in controlling blood pressure of severe early-onset pre-eclamptic patients.

STUDY DESIGN

Pre-eclamptic patients (n=47) with a gestational age (GA) between 21 and 32 weeks were treated with intravenous ketanserin in a maximum dosage of 14 mg/h, to obtain a diastolic blood pressure of 90 mmHg or below. The number of patients reaching and maintaining target blood pressure was retrospectively assessed. Patient characteristics associated with an adequate or inadequate response to ketanserin treatment were identified.

RESULTS

With a maximum intravenous dosage of ketanserin, target blood pressure was not achieved in 15 (32%) patients. A high systolic blood pressure at the start of treatment was significantly (p=0.02) associated with failure of ketanserin treatment. The median period of ketanserin treatment in the responding group was 3 days (range 1-10 days). In 26 (55%) of initially successfully treated patients, additional antihypertensive drugs had to be added to maintain adequate blood pressure control.

CONCLUSION

Intravenous ketanserin lacks antihypertensive efficacy in a substantial proportion of severe pre-eclamptic patients, despite high dosages. In patients who initially respond well to ketanserin treatment, additional antihypertensive treatment is often necessary to maintain adequate blood pressure control.

Pharmacological treatment of severe hypertension in pregnancy and the role of serotonin(2)-receptor blockers

Hypertensive disorders of pregnancy are the leading cause of maternal and perinatal mortality and morbidity in developing and developed countries. The etiology of preeclampsia is still unknown. Delivering the baby is the only definite treatment. The benefits of acute pharmacological control of severe hypertension prior to and/or post-delivery are generally accepted. Most drugs commonly used in the management of severe hypertension in pregnancy have significant maternal and/or neonatal adverse side effects. Furthermore, some are not effective to acutely lower the blood pressure in patients with a hypertensive crisis. Until recently not one of the commonly used antihypertensive drugs has been tailored to the pathophysiology of severe preeclampsia, being a clinical syndrome characterized by endothelial cell dysfunction, vasospasm and platelet aggregation. Ketanserin, a serotonin(2)-receptor blocker, is a drug that appears to be tailored for treating this pregnancy-associated enthothelial cell dysfunction. The results of several prospective trials show that there is a definite place for serotonin(2)-receptor blockers in the treatment of pregnancy-induced hypertensive disorders. This review provides a summary on the more established drugs as well as on some of the newer antihypertensive drugs used in pregnancy with emphasis on the existing experience with ketanserin.