Terminology

There are a number of terms that are used in describing the effects, both physical and psychological, associated with opioids (and also other substances). These terms are commonly used imprecisely, often conveying incorrect or confusing messages; both between professionals and between patients and healthcare staff.

Various definitions have been suggested ^1,2,3,4, but there is no universally accepted approach, and definitions are often defined by the user group for which they are developed. For the purpose of this resource, the following terms are intended to have reasonably clear and tightly defined meanings, and some terms are best avoided.

Primary Four terms

Tolerance – this is a three-sided term.

1. The reduction of effect that a substance has over time. This may refer to either the beneficial effect, or the side effects. (It is possible to maintain a beneficial effect and become tolerant of the side effects).
2. The second is often, but not uniformly,  some resumption of beneficial (and/or side effects) by increasing the dose.
3. That the doses used in a ‘tolerant’ individual are likely to be deleterious, or even fatal, to a substance naive individual.

When describing treatment changes in a ‘tolerant’ individual, it is important to clarify the change in dose, against the current dose and indicate the benefits anticipated.

Withdrawal

Withdrawal effects are the negative effects seen when the current dose of a substance has been reduced or stopped, especially if done rapidly.

These effects are commonly both physiological and psychological. They have the potential to cause harm, and must be recognised, counselled and managed appropriately.

Sudden cessation or dose reduction of opioids may cause rebound pain, which usually settles, but may be difficult to differentiate from the unmasking of pain due to a beneficial effect; and more general systemic effects such as abdominal pain/colic (which, again, might be a facet of the pain problem), diarrhoea, sweating, anxiety and acute mood changes.

Escalation

This is a two faceted term, which encompasses:

1. The rate at which tolerance to benefit has developed.
2. The rate at which the prescriber has increased the medication; obtaining the intended benefit, or a degree of it, again, and for it to then wane again.

Substance Misuse

There remains the difficulty of describing the use of substance without or beyond clinical indication/prescription instructions (usually in terms of dose). The description is one of judgment⁵, but is partially descriptive. It is often a ‘built-in’ part of the term ‘Addiction’ – see below, and other terms.

Associated Terms

Dependence: This is a mixed term

1. Psychological Dependence – This is an emotional issue. A ‘longing’ for the substance and its psychological effects (a sense of well-being), but not necessarily associated with physical withdrawal symptoms. It has significant psychosocial aspects.

May be confused with ‘craving’ – which is a desire for the substance driven by physical withdrawal.

2. Physical Dependence – This encompasses the concepts of; Tolerance, Withdrawal and Dose Escalation which usually provide better descriptions of the issues; with or without the additional term Substance Misuse which indicates a degree of inappropriate use.

Other terms

Addiction

This is difficult term, frequently used in a pejorative sense, with complex psychosocial implications.

It is commonly used as a broad term to encompass components of the terms Substance Misuse, Tolerance, Withdrawal, and Psychological Dependence; but is commonly used to describe very different aspects of its component parts, and without qualification, is generally best avoided.

Pseudo-addiction

This describes the use of, or seeking for, a medicine at a dose/frequency beyond the prescription, which may indicate an inadequate initial dose or the development of tolerance.

The embedded use of ‘addiction’ within the term makes it an often misunderstood term, and its clinical utility is often better served with consideration to the primary terms above.

Opioid use disorder

Opioid use disorder (OUD) is defined as the chronic use of opioids that causes clinically significant distress or impairment. Symptoms of this disease include an overpowering desire to use opioids, increased opioid tolerance, and withdrawal syndrome when opioids are discontinued. OUD can range from dependence on opioids to addiction.

References:

1. Definitions Related to the Use of Opioids for the Treatment of Pain -  A consensus document from the American Academy of Pain Medicine, the American Pain Society,and the American Society of Addiction Medicine. https://www.naabt.org/documents/APS_consensus_document.pdf (accessed February 2021)
2. https://www.cdc.gov/drugoverdose/opioids/terms.html
3. Joint Meeting of the Drug Safety and Risk Management (DSaRM) Advisory Committee and Anesthetic and Analgesic Drug Products Advisory Committee (AADPAC).    https://www.fda.gov/media/127780/download (accessed February 2021)
4. Acute Pain Management Scientific evidence ANZCAFPM 4^th ed(2015) p569. https://www.anzca.edu.au/getattachment/4c3b03b7-52bf-4c10-9115-83d827c0fc38/Acute-Pain-Management-Scientific-Evidence.aspx (accessed February 2021)
5. Access to treatment with controlled medicines rationale and recommendations for neutral, precise, and respectful language. W. Scholten et al. Public Health  1 5 3 ( 2 0 1 7 ) 1 4 7 - 1 5 3.