Zaditen (Novartis)
250 microgram/mL in 5 mL bottles
Approved indication: seasonal allergic conjunctivitis
Australian Medicines Handbook section 11.3 Correction.

Correction (June 2005)
Ketotifen hydrogen fumarate.
The recommended Australian dosage is one drop twice daily.

Ketotifen is an antihistamine which has been available overseas for many years. In addition to antagonising the H1 histamine receptors, ketotifen stabilises mast cells to prevent the release of inflammatory mediators.

Patients instil ketotifen eye drops two or three times a day. It is unclear how much of the drug is absorbed, but a therapeutic effect begins within a few minutes.

An Australian study compared ketotifen with placebo and levocabastine for one month. Although only half of the 109 patients given ketotifen responded, this was higher than the 41% response in the levocabastine group and significantly better than the 33% response in the placebo group.1

Olopatadine is another antihistamine which stabilises mast cells. Some comparisons favour olopatadine2 while others favour ketotifen.3 There appear to be no published comparisons of ketotifen and ophthalmic non-steroidal anti-inflammatory drugs.

The main adverse events in trials of ketotifen were conjunctival injection, headaches and rhinitis. Patients may also complain of burning or stinging in their eyes.

Although the mast cell stabilisers cromoglycate and lodoxamide can be used to prevent allergic conjunctivitis, they have to be given for a few weeks in advance of exposure to the allergen. Ketotifen is more suited to be one of the options for the short-term treatment of patients with symptoms of seasonal allergic conjunctivitis.

References

  1. Kidd M, McKenzie SH, Steven I, Cooper C, Lanz R. Australian Ketotifen Study Group. Efficacy and safety of ketotifen eye drops in the treatment of seasonal allergic conjunctivitis. Br J Ophthalmol 2003;87:1206-11.
  2. Aguilar AJ. Comparative study of clinical efficacy and tolerance in seasonal allergic conjunctivitis management with 0.1% olopatadine hydrochloride versus 0.05% ketotifen fumarate. Acta Ophthalmol Scand 2000;78:52-5. .
  3. Ganz M, Koll E, Gausche J, Detjen P, Orfan N. Ketotifen fumarate and olopatadine hydrochloride in the treatment of allergic conjunctivitis: a real-world comparison of efficacy and ocular comfort. Adv Ther 2003;20:79-91. .

Some of the views expressed in the following notes on newly approved products should be regarded as preliminary, as there may have been limited published data at the time of publication, and little experience in Australia of their safety or efficacy. However, the Editorial Executive Committee believes that comments made in good faith at an early stage may still be of value. Before new drugs are prescribed, the Committee believes it is important that more detailed information is obtained from the manufacturer's approved product information, a drug information centre or some other appropriate source.