Nifedipine or Procardia

Has anyone taken this medication before for Perterm Labor or "threatened" preterm labor. I was place onnthis med 24 hours ago.. it cause my blood pressure to drop. So the dr. Told me to stop taking them..so im a bit nervous my baby may be born early...my contractions yesterday were 2-3 minutes apart.. they couldnt stop them completely. So if anyone could offer up so advice or at least some information please let me know.. if you were on it how soon after you stop taking the meds did you go into labor

Thanks so much