Screening and assessment of sedating antihistamine use
Ask all new patients routinely and others (adolescents and adults) opportunistically and periodically about medication use, as part of a general screen for disorders of substance use and gambling; these disorders are common (and often co-exist) and patients are reluctant to disclose them, often due to fear of stigma. Screening and assessment of substance use and addictive behaviours outlines history-taking (including use of the ASSIST-Lite tool), examination, and investigations that should be considered in a broad review of substance use and addictive behaviour.
If sedating antihistamine use is identified, specific questions to assess use in more detail include:
- duration and dosage—prolonged use of recommended or higher doses can result in withdrawal symptoms on stopping
- use of any other substances (alcohol, over-the-counter medications, complementary therapies1, other prescribed or illicit drugs)—assess risk of fatal sedation or other dangerous interactions
- factors that precipitate or perpetuate use—assess for undertreated anxiety, difficulties with regulating emotional distress (eg in personality disorder), insomnia, other disorders of substance use and chronic itch
- withdrawal symptoms experienced on previous attempts to reduce usage.
Common withdrawal symptoms are anxiety, insomnia, irritability and cravings; they are similar to those the patient may have been seeking to relieve when starting the drug. Pre-existing anxiety increases the likelihood of severe withdrawal; anxiety that persists for more than 1 week after stopping sedating antihistamines is likely to reflect an anxiety disorder or difficulties with emotional regulation rather than persisting withdrawal. Other withdrawal symptoms include nausea, vomiting, headache, sweating and dizziness.