Dry mouth

Dry mouth (formally known as xerostomia) is a very common physical effect of a wide variety of psychoactive substances, especially diuretics (which increase the rate of urination). Psychoactive stimulants, especially those like amphetamines at common to higher doses, are known to reduce the glandular release of saliva in the mouth, which can cause tooth decay and gum disease over time. Ensuring proper hydration and electrolyte balance can help mitigate these symptoms.

Dry mouth is diagnosed based on the person's experience of the symptom, rather than the actual dryness of one's mouth. Other substances that can produce this effect include anticholinergics such as tropane alkaloids like scopolamine or diphenhydramine (DPH), cannabinoids such as THC (especially if one is smoking cannabis), opioids, antidepressant drugs such as the tricyclic antidepressants, SSRIs, as well as lithium. Benzodiazepines are also known to produce dry mouth, although to a significantly lesser extent.

Acute dry mouth is the subjective effect of having a dry-feeling mouth (often accompanied by a difficulty, and is most often simply the result of dehydration. It is also a common side effect of many substances, especially the combination of more than one substance which can produce or amplify already present experience of a dry mouth, which can interact significantly.

Chronic xerostomia or dry mouth syndrome is the regular and/or consistent experience of having a dry mouth. Other than physiological causes like decreased glandular saliva production or Sjögren's syndrome, the most common cause of chronic xerostomia is polypharmacy and/or the combination of more than one substance or medication that brings about the effect.

Treatments exist, such as Cevimeline or similar substance which stimulates the release of saliva. Drugs like Cevimeline are muscarinic agonists, selective to M1 and M3 muscarinic-acetylcholine receptors. A problem noted with repeated use of such treatments is the overall worsening of the dry mouth symptoms over time. If the body adjusts to having chemical assistance in increasing saliva production, cessation of treatment with the chemical can lead to physiological dependence wherein there is a rebound effect upon abrupt stopping of treatment. In general, if the cause of dry mouth is due to a psychoactive substance, medication, or combination, medical treatment is not recommended. As a basic harm reduction practice, one should be mindful to stay consistently well hydrated, avoid mouth breathing, and limit or substance drug use if the effect becomes uncomfortable, unmanageable, or persists even when not under the influence of a psychoactive substance.

Dry mouth as a substance effect is considered to be benign unless the effect is chronic and continues to bother or cause tooth/gum issues in the person experiencing it.