Many clinicians may be unaware of the use of nut oil as a vehicle within antipsychotic depot preparations. We report a case of possible coconut hypersensitivity which occurred during treatment with flupenthixol decanoate.

An elderly woman with a diagnosis of paranoid schizophrenia was commenced on a 3-weekly depot of flupenthixol decanoate (20 mg). After 5 months (seven injections), she complained of soreness and swelling around the injection site. The depot was subsequently administered at a different site and in a lower volume of oil. Within 1 hour, she experienced intense local irritation and a generalised pruritus. Her systemic symptoms began to resolve within 24 hours, but continued scratching at the injection site led to a localised infection. Since then she has refused further depot medication and is hostile towards psychiatric services. Enquiries revealed that all depot preparations of flupenthixol contain coconut oil.

The symptoms described by the patient might be attributable to a late hypersensitivity reaction to flupenthixol decanoate, but they may also be a manifestation of a previously undiagnosed coconut allergy. The patient has refused to be tested for specific immunoglobulin E antibodies to coconut and is guarded when questioned about her dietary habits. Although coconut hypersensitivity is relatively rare, coconut allergens show immunological cross-reactivity with both soy and walnut proteins (Reference Teuber and PetersonTeuber & Peterson, 1999). The prevalence of allergies to peanut and tree nut (e.g. walnut, brazil nut) is increasing (Reference Sicherer, Sampson and BurksSicherer et al, 2000). Similarly, the number of reported cases of hypersensitivity to sesame seed and sesame oil has risen in recent years (Reference Levy and DanonLevy & Danon, 2001). In sensitised individuals, non-ingestion exposure to food allergens results in less-severe reactions than are observed following inhalation or ingestion (Reference Sicherer, Furlong and DeSimoneSicherer et al, 1999).

Depot preparations consist of an ester of the antipsychotic drug in a solution of coconut oil (flupenthixol, zuclopenthixol) or sesame oil (haloperidol, pipothiazine, fluphenazine). Currently, the British National Formulary (British Medical Association & Royal Pharmaceutical Society of Great Britain, 2001) provides no information regarding the oils used in depot preparations. Individual drug datasheets can also be misleading: coconut oil is referred to as ‘vegetable oil’ in the flupenthixol datasheet. Although guidelines regarding the labelling of food products are sometimes seen as overinclusive, they allow consumers to make an informed choice. Depot medications are in widespread use, particularly in patients with a history of non-compliance (Reference Adams, Fenton and QuraishiAdams et al, 2001). To avoid further alienating such patients from psychiatric services, it is essential that both clinicians and patients are able to make informed treatment decisions. This can only occur if the constituents of depot preparations, particularly those relating to nut and seed products, are more clearly labelled.