Isosorbide DinitrateIsosorbideNadololPentaerythritol TetranitrateVasodilator AgentsDelayed-Action PreparationsEsophageal and Gastric VaricesCaptoprilNitrate ReductaseDouble-Blind MethodNitric Oxide DonorsNitroglycerinHydralazineErgoloid MesylatesGastrointestinal HemorrhageAzygos VeinOxyfedrineAdministration, SublingualHypertension, PortalNitratesPolyvinyls