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Open Access Research

Nimodipine, a calcium channel blocker, delays the spontaneous LH surge in women with regular menstrual cycles: a prospective pilot study

Dan Nayot1, Shany Klachook2 and Robert F Casper12*

Author Affiliations

1 Department of Obstetrics & Gynaecology, Mount Sinai Hospital, University of Toronto, 92 College Street, Toronto, Canada

2 Samuel Lunenfeld Research Institute, Mount Sinai Hospital, University of Toronto, Toronto, Canada

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Reproductive Biology and Endocrinology 2013, 11:7  doi:10.1186/1477-7827-11-7

Published: 7 February 2013

Abstract

Background

Currently GnRH analogue injections are used to prevent premature LH surges in women undergoing assisted reproductive technology. This was a pilot study to determine the safety and effectiveness of nimodipine, an oral calcium channel blocker, to delay the mid-cycle spontaneous LH surge in women with regular menstrual cycles.

Methods

Eight women with regular menstrual cycles self-monitored three consecutive cycles for the day of an LH surge by daily urine assay. The first and third cycles were observatory. In the second cycle, subjects took nimodipine 60 mg by mouth three times daily for four days, starting two days prior to the expected LH surge day based on cycle one.

Results

The LH surge day in cycle 2 (nimodipine) was significantly delayed in comparison to both observatory cycle 1 (15.5+/−3.4 vs 14.0+/−2.8 days; p = 0.033) and cycle 3 (15.1+/−3.5 vs 13.1+/−2.4 days; p = 0.044). There was no difference in the LH surge day between the two observatory cycles (13.4+/−2.4 vs 13.1+/−2.4 days; p = 0.457). Three patients experienced a mild headache.

Conclusions

There was a statistically significant delay in the spontaneous LH surge day in the treatment cycle in comparison to both observatory cycles. Nimopidine should be further investigated as an oral alternative to delay a spontaneous LH surge.

Keywords:
Premature LH surge; In-vitro fertilization (IVF); GnRH agonist; GnRH antagonist; Calcium channel blocker; Nimodipine