Liquid Medication - Phenytoin with link to prior prescription

{
  "resourceType" : "MedicationRequest",
  "id" : "medrx0312",
  "identifier" : [{
    "use" : "official",
    "system" : "http://www.bmc.nl/portal/prescriptions",
    "value" : "12345689"
  }],
  "priorPrescription" : {
    "reference" : "MedicationRequest/medrx0304"
  },
  "status" : "active",
  "intent" : "order",
  "medication" : {
    "concept" : {
      "coding" : [{
        "system" : "http://www.nlm.nih.gov/research/umls/rxnorm",
        "code" : "1313112",
        "display" : "phenytoin 25 MG/ML Oral Suspension"
      }]
    }
  },
  "subject" : {
    "reference" : "Patient/pat1",
    "display" : "Donald Duck"
  },
  "authoredOn" : "2015-01-15",
  "requester" : {
    "reference" : "Practitioner/f007",
    "display" : "Patrick Pump"
  },
  "reason" : [{
    "concept" : {
      "coding" : [{
        "system" : "http://snomed.info/sct",
        "code" : "230456007",
        "display" : "Status epilepticus (finding)"
      }]
    }
  }],
  "note" : [{
    "text" : "Patient should be counselled to ensure good dental hygiene"
  }],
  "dosageInstruction" : {
    "simple" : {
      "text" : "100mg (4ml) three times daily",
      "timing" : {
        "repeat" : {
          "frequency" : 3,
          "period" : 1,
          "periodUnit" : "d"
        }
      },
      "route" : {
        "coding" : [{
          "system" : "http://snomed.info/sct",
          "code" : "26643006",
          "display" : "Oral Route (qualifier value)"
        }]
      },
      "doseAndRate" : [{
        "type" : {
          "coding" : [{
            "system" : "http://terminology.hl7.org/CodeSystem/dose-rate-type",
            "code" : "ordered",
            "display" : "Ordered"
          }]
        },
        "doseQuantity" : {
          "value" : 100,
          "unit" : "mg",
          "system" : "http://unitsofmeasure.org",
          "code" : "mg"
        }
      }]
    }
  },
  "dispenseRequest" : {
    "validityPeriod" : {
      "start" : "2015-01-15",
      "end" : "2016-01-15"
    },
    "numberOfRepeatsAllowed" : 3,
    "quantity" : {
      "value" : 360,
      "unit" : "mL",
      "system" : "http://unitsofmeasure.org",
      "code" : "mL"
    },
    "expectedSupplyDuration" : {
      "value" : 30,
      "unit" : "days",
      "system" : "http://unitsofmeasure.org",
      "code" : "d"
    }
  },
  "substitution" : {
    "allowedBoolean" : true,
    "reason" : {
      "coding" : [{
        "system" : "http://terminology.hl7.org/CodeSystem/v3-ActReason",
        "code" : "CT",
        "display" : "Continuing therapy"
      }]
    }
  }
}