Medication interactions

It is important for AOD workers to be aware of the complex and dynamic relationship between AOD use, mental disorders, and prescribed medication (i.e., the potential interactions between AOD use and prescribed medications and the ways in which AOD use and prescribed medication can affect each other). During the assessment phase, workers should explore the influence of prescribed medication on AOD use and vice versa. This clarification will contribute to a comprehensive management and treatment plan, with appropriate goals [389].

Table 38 provides some of the interactions between AOD and prescription medication, but this list is not exhaustive. For example, the selective serotonin reuptake inhibitors (SSRIs) fluoxetine and fluvoxamine have been shown to affect the metabolism of methadone and buprenorphine, with the discontinuation of fluvoxamine associated with opiate withdrawal [791]. In cases where withdrawal is unexpected, it is possible that the client may engage in other AOD use (or decrease treatment adherence) to cope with withdrawal symptoms, highlighting the need for worker awareness of the potential for such interactions. Similarly, central nervous system depressants not only increase the potential for overdose and respiratory depression when taken with each other (e.g., benzodiazepines, alcohol, opiates), but also increase the risk of overdose when taken with medication [792]. As described in Chapter B1, the compounds found in tobacco smoke can increase the rate some psychiatric medications, such as olanzapine and clozapine, are metabolised. This means people who smoke may need to be prescribed higher doses to achieve the required therapeutic dose of these medications, while those who are intending to reduce or quit smoking need to be carefully monitored and their doses reduced to avoid potential toxicity [230–232].

Interactions are also possible with other non-psychiatric medications. For example, alcohol increases the potential for stomach ulcers and bleeding when combined with steroids or other anti-inflammatory medications due to the combined toxic effects on the stomach lining [793]. Interactions with dietary supplements are also possible: as mentioned in Chapter B7, St John’s Wort has been shown to have significant interactions with a range of other medications including SSRIs and related drugs, oral contraceptives, some anticoagulants, immunosuppressants, and some cardiac medications [794].

TCAs = tricyclic antidepressants; MAOIs = monoamine oxidase inhibitors; SSRIs = selective serotonin reuptake inhibitors. Adapted from NSW Department of Health [431].

As such, when managing and treating clients with co-occurring AOD and mental health conditions, AOD workers need to take into account the level and type of AOD used (especially alcohol), as these may [795]:

• Alter the metabolism of prescribed medication.
• Decrease the effectiveness and/or increase the potential for side effects.
• Warn the client about potential interactions between substances of misuse and prescribed medication.
• Discuss the problems and potential dangers of using non-prescribed AOD to counteract the effects or side effects of prescribed medication.

It is important to note that polydrug use, and the variation in compounds contained in drugs that are manufactured illegally, may make it difficult to clarify and assess potential drug interactions [431, 796, 797]. In instances where workers are unable to determine if a medication will interact with AOD use, medication should be titrated, starting with a low dose [798].