Dosage with a Pre-Condition - Alprazolam

{
  "resourceType" : "MedicationAdministration",
  "id" : "medadmin0311",
  "contained" : [{
    "resourceType" : "Medication",
    "id" : "med0304",
    "code" : {
      "coding" : [{
        "system" : "http://www.nlm.nih.gov/research/umls/rxnorm",
        "code" : "308047",
        "display" : "alprazolam 0.25 MG Oral Tablet"
      }]
    }
  }],
  "status" : "completed",
  "medication" : {
    "reference" : {
      "reference" : "#med0304"
    }
  },
  "subject" : {
    "reference" : "Patient/pat1",
    "display" : "Donald Duck"
  },
  "occurrencePeriod" : {
    "start" : "2015-01-15T22:03:00+01:00",
    "end" : "2015-01-16T02:03:00+01:00"
  },
  "performer" : [{
    "actor" : {
      "reference" : {
        "reference" : "Practitioner/f007",
        "display" : "Patrick Pump"
      }
    }
  }],
  "reason" : [{
    "concept" : {
      "coding" : [{
        "system" : "http://snomed.info/sct",
        "code" : "266599000",
        "display" : "Dysmenorrhea"
      }]
    }
  }],
  "request" : {
    "reference" : "MedicationRequest/medrx0305"
  },
  "dosage" : {
    "text" : "0.25mg PO every 6-12 hours as needed for menses from Jan 15-20, 2015.  Do not exceed more than 4mg per day",
    "route" : {
      "coding" : [{
        "system" : "http://snomed.info/sct",
        "code" : "26643006",
        "display" : "Oral Route"
      }]
    },
    "dose" : {
      "value" : 1,
      "unit" : "TAB",
      "system" : "http://terminology.hl7.org/CodeSystem/v3-orderableDrugForm",
      "code" : "TAB"
    }
  }
}