'Nil by mouth' medication dose calculators and guidelines
There are 2 medication calculators in use by doctors, nurses and pharmacists who are looking after patients with Parkinson's who have been admitted to hospital and are unable to take their medications orally.
This page provides information on both calculators.
- Inpatient care and medicines management
- Treatments and medication
- Tools
- Doctor (Geriatrician)
- Doctor (Neurologist)
- Doctor (Other)
- Nurse (other)
- Nurse (Parkinson's nurse)
- Pharmacist
- Complex
- End of life
URGENT OPTIMAL update
The north west medicines safety officer (NWMSO) issued a rapid shared learning notice on 23 April 2025. The OPTIMAL tool is producing dosing errors. The owners have been notified by the NWMSO. We'll update this page with further details once a reply has been received.
There are 2 medication calculators currently in use by healthcare staff for patients with Parkinson's who are unable to take their medications orally.
The 2 calculators can give different dosage conversions. Calculators should be used consistently between prescribing staff working with the same patients. Always refer to local guidance from your Parkinson's service on which calculator to use before prescribing.
The 2 calculators are:
- PDMedCalc: Parkinson's 'nil by mouth' medication dose calculator (pdmedcalc.co.uk)
- OPTIMAL Parkinson's calculator and guideline (parkinsonscalculator.com)
There is information about both calculators below.
Parkinson's services are encouraged to document which calculator is recommended for use with their patients and to make this documentation readily available for non specialist staff.
Although PDMedCalc received an Excellence Network project grant towards its update, we do not recommend the use of one calculator over the other. We recommend that you thoroughly read the purposes of both calculators and use your clinical judgement when deciding which one to use. Find out more about Excellence Network projects grants.
PDMedCalc: PD 'nil by mouth' medication dose calculator
Disclaimer
This tool is no substitute for clinical reasoning nor should it be used as a substitute for expert advice. Please ensure you liaise with your local Parkinson's and pharmacy teams about any patient with Parkinson's who is unable to take their usual medicines.
Extensive effort has been made to ensure this tool is as accurate as possible, however the accuracy and completeness of the information provided can't be guaranteed.
The tool should therefore be used as a guide, with no medical decision being solely made on the results provided by this tool.
Who is this tool for?
Doctors, nurses and pharmacists who are looking after patients with Parkinson's who have been admitted to hospital and are unable to take their medications orally.
What is the purpose of the tool?
- Suddenly stopping Parkinson's medications can be extremely dangerous and due to the risk of neuroleptic malignant syndrome, potentially even fatal.
- In patients unable to take their usual Parkinson's medications orally, this tool is designed to convert a patient’s usual Parkinson's medications to a ‘Levodopa equivalent dose’ (LED).
- The LED is then used to calculate the dose of dispersible madopar to be given via a nasogastric tube to provide a patient with their usual amount of Parkinson's medication.
- The tool also provides a conversion to a rotigotine patch dose, as an alternative to nasogastric dispersible madopar. A correction factor is applied to avoid large rotigotine patch doses, as these may cause side effects such as confusion, hallucinations or delirium.
- Amantadine can be safely omitted if swallow is compromised.
- If the patient is on a subcutaneous Apomorphine infusion, Duodopa (via PEJ) or a subcutaneous ProDuodopa infusion (foslevodopa/foscarbidopa) no conversion is required; please continue to use their existing non-oral treatment.
Where did this tool come from?
The development of the tool was led by James Fisher and the Northumbria Healthcare NHS Foundation Trust Parkinson’s Disease team in 2014, who worked in collaboration with Daniel Jamieson (Computing Science PhD student at Newcastle University).
The tool was redeveloped in 2024 with support from TPXimpact and funding from an Excellence Network project grant.
PDMedCalc was registered with the UK Medicines and Healthcare products Regulatory Agency (MHRA) as a Class 1 medical device on 15 February, 2024.
If you have any questions about PDMedCalc, please contact [email protected].
Note for people with Parkinson's
This resource is intended for use by professionals only. People with Parkinson's are advised to consult with their specialists before making any changes to their medication.
The PD Med Calc information on this page was last reviewed in March 2024.
OPTIMAL Parkinson's calculator
URGENT: The north west medicines safety officer (NWMSO) issued a rapid shared learning notice on 23 April 2025. The OPTIMAL tool is producing dosing errors. The owners have been notified by the NWMSO. We will update this page with further details once a reply has been received.
Read the rapid shared learning notice.
What is the purpose of the tool?
The OPTIMAL guideline and calculator aims to help non specialist clinical staff to better manage patients with Parkinson's when they are admitted to hospital in an emergency, better plan for elective admissions and direct staff to sources of specialist support.
Who is this tool for?
The guideline and conversion calculator is for non specialist clinical staff who need to manage their patient's Parkinson's medication until support is available from their local Parkinson's specialist or pharmacist.
It is not intended to replace locally agreed guidelines and prescribing practices, but rather offer guidance until specialist advice can be obtained.
Where did this tool come from?
The guideline and calculator have been developed by a team of Parkinson's specialists and pharmacists, with the support of the Wessex Parkinson's UK Excellence Network and the British Geriatrics Society Movement Disorders Section. The principal developers are:
- Dr Gayle Strike, Consultant Geriatrician, University Hospital Southampton NHS Foundation Trust
- Dr Naomi Fox, Consultant Geriatrician, Poole Hospital NHS Foundation Trust
- Mr James Allen, Senior Pharmacist, University Hospital Southampton NHS Foundation Trust
- Mr Ben Fox, Software Engineer
The last update to this tool was in March 2022 with the next due March 2023.
Note for people with Parkinson's
This resource is intended for use by professionals only. People with Parkinson's are advised to consult with their specialists before making any changes to their medication.