Changing "add new node" button
You can use hook_field_widget_WIDGET_TYPE_form_alter() to alter the button name

example: 


/**
 * Implements hook_field_widget_WIDGET_TYPE_form_alter().
 */
function example_field_widget_inline_entity_form_form_alter(&$element, &$form_state, $context) {
  // Rename the button in specific form.
  if($form_state['build_info']['form_id'] == 'eck__entity__form_edit_sample_sample') {
    $element['actions']['ief_add']['#value'] = t('Add new medecine');
  }
}