Cognitive & neuro

Intranasal insulin

Ordinary insulin sprayed into the nose to reach the brain, studied for memory and Alzheimer's with mixed results.

Limited evidenceInvestigationalAdd to compare

What it is

Intranasal insulin is the hormone insulin delivered as a nasal spray, with the aim of reaching the brain along the olfactory and trigeminal pathways before much of it enters the bloodstream. The idea rests on insulin receptors in the hippocampus and cortex. It is not an approved treatment for any cognitive condition; it has been studied in academic trials for memory and Alzheimer's disease.

How it works

1
Insulin receptors are dense in the hippocampus and cerebral cortex and are involved in synaptic plasticity.
2
The nasal route delivers insulin to cerebrospinal fluid within about 15 to 30 minutes in studies.
3
Functional imaging shows increased hippocampal and prefrontal activity after nasal doses.
4
Reported modulation of amyloid and tau handling in cell and animal work.
5
Systemic absorption is limited, which is why hypoglycaemia is uncommon but possible.

What it's studied for

Amnestic mild cognitive impairment

Mild to moderate Alzheimer's disease

Memory in healthy adults

Cognition in type 2 diabetes

Large multicentre trials of nasal insulin in Alzheimer's disease

Reported and studied effects

Some single-centre trials reported improved delayed verbal memory and preserved brain glucose metabolism
Larger multicentre trials showed modest or no overall benefit
Results across studies are inconsistent, with responders not predictable
Occasional mild hypoglycaemia

Research protocol notes

Research context only

Research context only - investigational. Trials typically used 20 to 40 international units once or twice daily through a metered nasal device for 4 weeks to 12 months, with delayed recall and brain imaging as endpoints, and blood glucose monitored because a fraction is absorbed.

These figures are described so you can understand what researchers did. They are not a dose, a schedule, or a suggestion — and they are not a substitute for a doctor.

Possible side effects and contraindications

Safety profile

Possible side effects

Nasal irritation and runny nose
Mild hypoglycaemia in a minority
Headache
Hypokalaemia with high systemic exposure

Contraindications and cautions

Recurrent hypoglycaemia
Significant nasal or sinus disease
Not for anyone without glucose monitoring in a trial setting
Pregnancy and childhood - untested

A side-effect list is never complete, and these are not the only situations that warrant caution. Anything unexpected, or anything you are unsure about, should be discussed with a doctor before use.

Evidence assessment

Limited evidenceSmall human studies or animal data only

Small human studies or animal data only

Several randomised trials exist but they are small and disagree; the larger multicentre studies did not confirm the memory benefits seen in single-centre work.

References

References link to published literature, regulator pages or literature indexes. Where a link points to a search, it collects the peer-reviewed work on that molecule rather than a single study.

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