The story of a 75-year-old man.
A woman in her 70s wanted to have a consultation about her husband who has recently been introduced to Lantus and is experiencing nightly diarrhoeas few hours after injecting. Her husband (who was not with her for the consultation) is due an eye surgery. He has suffered diabetes for years and is taking low dose alogliptin and metformin to control his high blood sugar levels. However, during a review consultation with the eye specialist, it was agreed that he goes on an insulin to lower his blood sugar to below 10 mmol/L consistently before the procedure can be done.
Lantus is a brand name for a long-lasting insulin known as insulin glargine. It is injected once a day (mostly before the evening meal) and provide 24-hour basal insulin as happens in the normal human insulin secretion. The description of the undesirable effects of Lantus does not contain persistent diarrhoea after injection.
The woman had made several attempts to contact his husband’s General Practitioner (GP) without any success. She called 111 helpline who referred her to Diabetes UK (a non-governmental NGO) supporting diabetic patients. They too informed her they do not think the Lantus has anything to do with the diarrhoea and left it like that. She and her husband are confused and have no idea who to turn to for help. So, she had come to seek my professional opinion as a pharmacist.
How do we resolve this? First and foremost, according to the literature, there is no direct or indirect link between injecting Lantus and diarrhoea. However, we humans are not identical in terms of how we react to medications. The fact that there is no documented link does not preclude the insulin for being the cause of the diarrhoea.
Secondly, there is a high risk of severe nocturnal hypoglycaemia if the old man continues to experience watery diarrhoea every evening after injection. So, a solution needs to be found. I attempted to contact the surgery to express my concern of hypoglycaemia with the GP but had to give up after being put on hold for more than 10 minutes. Community pharmacy is a very busy place with several things going on simultaneously and it is difficult to hold onto a phone for long when others waiting for their medications to be checked, vaccinations to be done and more consultations in the queue.
But I could not signpost this woman any longer, she looked exasperated that the primary healthcare system was failing her husband with a potential risk of serious health consequences. We came to a consensus that the woman should advise her husband to suspend the insulin injection for one night and see if the diarrhoea would stop. If it does, then we can confidently attribute the diarrhoea to the insulin and other options would have to be considered. If the diarrhoea does not stop even after suspending injection of the insulin, then other causes of the nightly diarrhoea would need to be investigated. This would still not reduce the risk of severe hypoglycaemia for this old man even though insulin glargine provides only basal insulin in the blood stream.