France. Adverse reactions can be caused by excipients, which include preservatives, stabilisers, colourants, sweeteners, and aromatics. Some of the main reactions reported are listed below:

• Asthma, anaphylaxis, local irritation. Sulfites are frequently used preservatives. They can cause hypersensitivity reactions such as asthma, general rash and anaphylactic shock. Sulfites have been withdrawn from the composition of several medicines intended for asthmatic patients since these patients experience the most severe reactions to sulfites. However, there are still some products on the market in France that are indicated for asthma and contain sulfites, e.g. injectable betamethasone (Betnesol) or dexamethasone (Soludécadron).

• Benzalkonium chloride is another preservative used in suspensions and solutions for nasal sprays and in eyedrops. In nasal sprays this product can exacerbate rhinitis and in eyedrop preparations it can induce irritations or keratitis. Several eyedrop preparations now exist without a preservative, either in single dose bottles or in bottles equipped with an antibacterial filter.

• Risk of teratogenicity. In 1995, a preparation of erythromycin, topical solution (Erythromycine Balleul) was withdrawn from the market because of its high content of 2-ethoxyethanol (ethylglycol), a substance easily absorbed by the skin which is known to be teratogenic to animals and to alter spermatogenesis.

• Misuse. Serious incidents can occur when a product is administered by a route for which it is not intended and for which the excipient is not adapted, for example, drug addicts may crush tablets and then inject them; or a product containing benzyl alcohol which is not intended to be injected intrathecally may be administered by this route (risk of paraplegia).

Doctors are reminded to consider excipients when a patient experiences an adverse reaction after taking a medicine, and especially if several different medicines are concerned.

Reference: La Revue Prescrire 18 (187): 595 (1998).