Older male man lies on a bed with his worried wife sitting with him, holding his hand.

Unintentional overdose of morphine sulfate oral solution


The national investigation

This is a short investigation that looks at one local incident.

Although this didn’t meet our criteria to carry out a full national investigation, we felt it would be valuable to demonstrate the analysis we carry out before launching a national investigation. This analysis shows how we undertake a systems-based investigation.

Systems-based investigations examine all of the factors that in combination contribute to a patient safety incident happening, rather than looking to attribute blame for errors to individuals.


The aim of this investigation report is to help improve patient safety in relation to the use of oral morphine sulfate solution (a strong pain-relieving medication taken by mouth). It also aims to demonstrate the systems-based approach that HSIB uses to identify matters for national investigation, via a scoping investigation into a patient safety incident (referred to here as the ‘reference event’).

The reference event concerned Len, who took an accidental overdose of morphine sulfate oral liquid. Len’s family referred their concerns to HSIB to consider whether Len’s care highlighted any national safety issues that could be addressed through an HSIB investigation.

The results of the scoping investigation did not meet the criteria for a national investigation. However, HSIB thought it would be beneficial to publish a shorter investigation report highlighting specific risks which may be associated with morphine sulfate oral liquid and to improve understanding of and engagement with HSIB investigations.

Reference event

Len, who was 89 years old, fell at home and developed pain in the right side of his chest. Len had previously been diagnosed with Charcot-Marie-Tooth (CMT) disease, which is a progressive disease that affects the nervous system.

Len developed breathing problems so contacted his GP practice by telephone. The GP asked Len some questions about his symptoms and offered him a face-to-face appointment that afternoon. At that appointment, the GP ruled out a chest infection, prescribed additional ibuprofen and told Len to continue taking paracetamol.

Len’s family later called an ambulance because Len was very breathless and in pain. Len was taken to the emergency department at his local hospital. He was assessed by medical staff who diagnosed a suspected rib fracture. He was given additional pain relief. However, after returning home Len found that the lidocaine pain relief patches he was given irritated his skin and he stopped using them.

Len’s family noticed that over the next 2 weeks he became quieter and less active.

Len again contacted his GP with ongoing breathlessness and pain. The GP prescribed Len morphine sulfate oral solution, which has a concentration of 10mg in 5ml, at a dose of 1.25ml to 2.5ml (which equates to 2.5mg to 5mg per dose) to be taken up to every 4 hours when required. Len’s Wife collected the morphine solution from the pharmacy for him and Len took three doses of 5ml (10mg) morphine (two to four times the suggested dose) over the course of the day. Len and his Wife thought that the 10mg in 5ml strength on the manufacturer’s label on the morphine bottle showed the correct dose.

The next morning Len’s Wife could not wake him and called an ambulance. Len was taken to the emergency department with breathing difficulties, thought to be caused by a suspected accidental overdose of morphine, pneumonia and worsening of his CMT. Len initially recovered after receiving treatment, but a short time later was found to be unresponsive and was pronounced dead.

After his death, Len’s GP phoned the family to offer their condolences. It was only when the family asked why Len had been prescribed such a high dose of morphine that it became clear that Len and his Wife had not seen the dispensing label on the outer packaging advising Len to take 1.25ml to 2.5ml.


The key findings from the investigation include:

  • The initial choice of paracetamol and ibuprofen to control Len’s pain following his fall was in line with national guidance.
  • Len’s pain was not effectively controlled on paracetamol and ibuprofen, therefore required review by his GP to address this.
  • The choice of a morphine liquid was in line with national guidance and a reduced morphine dose was prescribed in line with recommendations for the older person and Len’s degree of kidney dysfunction.
  • Len’s dose of morphine was displayed on the dispensing label attached to the outer box that the morphine was provided in. The label was not seen by Len or his Wife.
  • Len and his Wife read the manufacturer’s text on the morphine bottle, which showed the strength of the morphine liquid, and understood this to be the required dose.
  • When Len was taken to hospital with difficulty with breathing, he was found to have taken an accidental dose of morphine, he had a chest infection and his CMT may have impacted on his breathing.