Drugs to treat diabetic retinopathy
Introduction
Growth factor inhibitors are new, and there are new reports each week, and these are very exciting times. All ophthalmologists treating these conditions are frustrated they cannot use these drugs as they would wish. See one here.
The drugs have not yet been extensively investigated, so they are not licenced. Further research is desperately needed. Hopefully the drugs will prove very helpful.
- However, all these drugs are likely to have a temporary benefit. So until a long lasting formulation arrives, they will almost certainly have to be given AS WELL AS laser.
- These are given as injections into the eye, and are summarised here.
- These 3 injections will be much more effective if the macular oedema is relatively new, and much less effective if it has been present >6 months.
- All have to be given in a very clean minor-operations room or operating theatre
- all have a 1/1000 risk of very severe eye infection which can be blinding, but can be treated if caught early see
- there is 1/100 risk of other problems such as retinal tear
- triamcinolone causes eye pressure rise
- all may cause a pressure rise in the first 1-2 hours
- prices quoted below are cost of the drug itself.
- many ophthalmologists are learning how to use these drugs, as they are new
- Many experts treating very advanced DR that presents late in the disease believe these drugs should be given at the onset, and then laser or vitrectomy surgery & endo laser carried out 1-4 weeks later
A comparison
- Avastin is the cheapest and most popular in the US. See some new links for Avastin. Avery et al. With vitreous haemorrhage. Rubeosis. Disc vessels.
- Macugen has the most research supporting it, but is expensive. It has passed its phase 2 trials, with another paper here
- Triamcinolone is cheap and available but causes a rise in eye pressure in 10-50%, and is probably the least effective. Triamcinolone may reduce macular oedema more effectively.
summary |
advantages |
disadvantages |
|
IVT
Intravitreal triamcinolone
details |
this is a steroid, and works by reducing inflammation | funding available benefit lasts 3 months sight improves a little in 50% |
|
IVA
Intravitreal avastin
details |
this blocks the effect of the 'growth factor' VEGF that causes leakage and new vessel growth | safer than IVT as no long term pressure rise main effect 1 month |
|
IVM
Intravitreal macugen
details |
This is a similar drug to avastin. | more research than avastin showing benefit. main effect 1 month |
|
Funding not available
Most hospitals in the UK obtain funding from Primary Care Trusts (PCT), and most PCTs have refused large scale funding. Good Hope has been offered funding for maclar oedmea patients, but thiw is awaited. A few patients were treated for proliferative retinopathy, which helpded when given in addition to laser.
Avastin costs as above are mainly related to the costs of the procedure: it has to be given as an injection into the eyeball in the operating theatre or very clean room. Avastin treatment is routine in the US.
If you are a patient it would be helpful if you would write to your MP and ask for funding to investigate the use of Avastin in diabetic retinopathy.
Repeated injections
Unfortunately the effect of these drugs is not long lived, as in the table above. Here is my interpretation of Macugen's results:
Visual acuity improved whilst the injections are given, but starts to deteriorate when they are stopped. However, if the blood pressure is lowered aggressively and diabetic control improves, ophthalmologists hope for much longer benefit.
Systemic treatment (tablets etc)
ARB/ACEI blockers and fibrates help. Porta 2011
Somatostatin in retinopathy
Previous reports indicated that this drug would be helpful see , but there are few reports other than case reports. More recent reports indicate no long term benefit.
Good control of diabetes
This is essential even with the new drugs. See targets.