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Switching from monitored dosage systems to original packs

For prescribers and all staff responsible for administering medications in care homes.

You can download a full pdf version of this document by following the link on the right.

What is a monitored dosage system?

It’s a medication storage device that helps to dispsense medicines adherence to individual patients. An MDS device is prepared by trained pharmacy professionals who repackage and dispense prescribed medications into the storage device.1 Original packs (OP’s) aren’t repackaged or re-dispensed. They’re supplied to patients in the original medicine’s container.


The concerns surrounding patient safety and effectiveness around medicines supply in MDS devices aren’t new. Guidance from the Specialist Pharmacy Service (SPS)2 and Royal Pharmaceutical Society (RPS) called for the change of supply of medicines to original packs to be promoted as a standard.3

The majority of published evidence refers to the care home setting where using MDS saves staff time and can cause fewer administration errors than manufacturers’ original packaging.4

The National Pharmacy Association (NPA) had reports of several errors. MDS trays prepared in advance by the pharmacy have been given or incorrectly dispensed to the wrong patients resulting in both fatalities and serious harm.5

The most prominent published case of errors reported in 2016 identified 22 instances where a cause of death listed methotrexate medication errors from national error reporting data.6 It’s likely that adverse patient safety reports involving MDS are under reported and so a lack of reports doesn’t imply patient safety.


Our aim is to:

  • provide guidance that supports safe administration of medications when care homes are changing from MDS to original pack administration
  • highlight key issues to consider when care home staff administer medications from original packs.


Staff members should have robust training on administering medication from OPs before the changeover. Care home medication policies will need updating 7. Local community pharmacies will provide care homes with support during the process of transitioning.

Stock balance checks

Open one box at a time

On receipt of medication with multiple packs, only open one box should at one time. The remaining boxes should remain sealed until needed. This ensures that during stock checks, these can be accounted for as the full quantity stated on the box without having to open it.

Separate part-used from unused whole strips

For packages of medications with lots of strips, for example, paracetamol, use an elastic band to separate the part-used strip from the unused whole strips. This will help to simplify the stock counting process for this medication.

Do fortnightly stock balance checks

These should be done as good practice, ideally on a fortnightly basis. This should happen at the beginning and end of each cycle. If this highlights any discrepancies, then you’ll need further counts mid-cycle.

Do more frequent counts when you move to OPs

We recommend this when first moving to original packs. Reduce counts over the course of the first month if there are no discrepancies.

Exceptions to fortnightly checks

These include medications such as warfarin or any controlled drugs. You should so these stock counts each time you administer the medication to a resident to make sure you pick up any discrepancies relating to these medications immediately.

Do not hold excess stock

We don’t encourage excess stock holding. 8  But if you do have any, you should lock it away and not put it into use until needed.

You should still include it in the regular stock balance checks.

Calendar packs

If the original pack is a calendar pack (day specific blisters), staff members should check that the patient has that tablet on the correct day. If the days don’tt match up, this should trigger a full stock count on that item sooner than when the scheduled balance check is due.

Benefits of changing to original packs9

These include:

  • maintainance of the residents’ dignity and independence
  • enclosed patient information leaflet in each individual pack for reference and information
  • identification of the medicine from the original packs
  • reduction of medicines waste
  • ease of amending medications following changes or if a medicine is stopped
  • lower risk of infection
  • less space compared to MDS.


  1. PSNI Monitored Dosage Systems.
  2. Oboh L. Supporting older people in the community to optimise their medicines including the use of multi compartment compliance aids (MCAs). Specialist Pharmacy Services 2015. 3. Royal Pharmaceutical Society. Improving Pharmaceutical Care in Care Homes.
  3. Oboh L. Monitored dosage systems are not the only solution for older people. The Pharmaceutical Journal 2007; 278(7453):606.
  4. National Pharmacy Association. Common dispensing errors resulting in indemnity claims (UK) – superintendent update July 2019.
  5. Cairns R, Brown JA, Lynch AM et al. A decade of Australian methotrexate dosing errors. Med J August 2016; 204(10):384.e1-384.e6.
  6. Effective record keeping and ordering of medicines | Quick guides to social care topics | Social care | NICE Communities | About | NICE
  7. Reducing medicines waste guidance
  8. PresQUIPP. Changing from medicines dispensed in monitored dosage systems (MDS) to original packs (OP) in care homes – April 2020.