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Scenario: Reformulation reaction

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Scenario: Reformulation reaction

Hugh Trelfer is collecting his repeat medication and asks to speak to pharmacist Parveen about a reaction he had to his eye drops...

“Those Xalatan eyedrops you gave me last time didn’t half sting, Parveen,” he says. “I’ve been using them for years without any problems, but this lot were so bad I thought about stopping them altogether!” Parveen tells Hugh that she thinks she knows what the problem is. “I can report the side-effect you have had from the drops and I’ll also speak to your GP about changing them. Leave it with me.”

What’s happened?

Hugh seems to be suffering from eye irritation as a result of Xalatan eye drops (latanoprost) being reformulated in order to get rid of refrigeration as a storage requirement. Although the change was made in 2013, long expiry dates and stock rotation procedures mean that some patients are only now receiving the reformulated product, which contains eye drops at a pH of 6.0, a decrease of 0.7 from the previous form of the product.

In the year before the reformulated product became available, no Yellow Card reports of eye irritation were filed for patients on Xalatan, but 22 reports were made in the following year. Parveen is planning to complete a Yellow Card report about Hugh’s experience and, either consult with the GP about an alternative for his glaucoma, or refer Hugh back to the GP for a treatment review.

The bigger picture

Prostaglandin analogues, the class of drug to which latanoprost belongs, are considered first-line treatment for early or moderate chronic open angle glaucoma (COAG), where the patient is at risk of significant visual loss during their lifetime. The drug reduces intraocular pressure (IOP) by increasing the flow of humour out of the eye.

Other drug treatments that may be used for COAG include beta-blockers, carbonic anhydrase inhibitors and sympathomimetics, sometimes concurrently in order to achieve the patient’s target IOP. If these fail or are not tolerated, laser trabeculoplasty or surgery may be considered. Regular monitoring – anything from every two months to once a year – is needed.

Extend your learning

  • Sign up to receive email updates from the MHRA about drug safety alerts gov.uk/drug-safety-update
  • NICE recommends checking instillation technique in people with COAG who do not experience an adequate reduction in IOP following pharmacological treatment. Refresh your knowledge of this area by reading the Nursing Times article here
  • Patients prescribed latanoprost or another prostaglandin analogue for the first time should be counselled on a very specific side-effect that may occur. Check what this is by reading the relevant information under ‘Prostaglandin analogues and prostamides’ in chapter 1.6 of the BNF, which can be accessed here (registration required).
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