Patients in advanced stages of cancer or with other serious illnesses often suffer from severe pain, against which simple measures such as cold or heat applications are no longer effective. The use of effective painkillers (analgesics) is then necessary. The World Health Organization (WHO) has drawn up a step-by-step scheme for this drug-based pain therapy, which is intended to help doctors treat patients optimally according to their needs.
Pain therapy: WHO DNA rule
WHO experts recommend the so-called DNA rule for drug-based pain therapy:
- D = By mouth: Oral painkillers should be given preference wherever possible (e.g. over painkillers that have to be injected). Administration via the anus (rectally), under the skin (subcutaneously) or as an infusion into a vein (intravenously) should be considered if oral administration is not possible.
- N = After the clock: The analgesics should be given at fixed intervals depending on the duration of action – always when the effect of the previous administration ends.
- A = Analgesic regimen: When prescribing analgesics, the so-called WHO staged regimen should be taken into account.
WHO step-by-step pain therapy scheme
Level 1 painkillers
The first level provides for simple painkillers – so-called non-opioid, i.e. non-morphine-like painkillers. In contrast to the opioids of WHO levels 2 and 3, non-opioid analgesics do not have a narcotic (anaesthetic) effect and do not impair the patient’s ability to perceive. They also do not pose a risk of addiction. Some of these painkillers are therefore also available without a prescription.
Examples of non-opioid painkillers are paracetamol, metamizole and the so-called NSAIDs (non-steroidal anti-inflammatory drugs) such as acetylsalicylic acid (ASA), diclofenac and ibuprofen. They have varying degrees of analgesic (pain-relieving), antipyretic (fever-reducing) and anti-inflammatory (antiphlogistic) effects.
However, paracetamol and acetylsalicylic acid are not suitable for use in tumor pain according to the current practice guidelines of the German Society for Pain Medicine.
When dosing non-opioid analgesics, the so-called ceiling effect must be taken into account: Above a certain dose, pain relief cannot be increased any further – at most, the risk of side effects then increases as the dose is increased further.
Level 2 painkillers
According to the WHO, the second level of pain therapy involves weak to moderately strong opioid painkillers such as tramadol, tilidine and codeine. Opioids are good painkillers, but have a narcotic effect, which means they can impair perception and can also be addictive. Other side effects of weakly effective opioids include constipation, nausea, vomiting, dizziness and fatigue.
According to the German Society for Pain Medicine, tramadol and tilidine should only be given on a short-term basis for days or weeks before switching to a level III preparation.
A combination of weak opioids with first-level painkillers can be useful because they have a different mode of action than opioids. This can significantly improve the overall pain-relieving effect.
As with first-level painkillers, the ceiling effect can also occur with weak opioids.
Level 3 painkillers
If necessary, strong opioids can be given together with first-level painkillers. However, they should not be combined with each other (e.g. morphine and fentanyl) or with weak second-level opioids.
Almost all strong opioids cause persistent constipation as a side effect. Nausea and vomiting are also common. Other side effects include respiratory depression, sedation, itching, sweating, dry mouth, urinary retention or involuntary muscle twitching. Most side effects occur at the start of treatment and when the dose is increased.
Co-analgesics and adjuvants
At all stages of WHO pain therapy, so-called co-analgesics and/or adjuvants can be given in addition to the painkillers.
Co-analgesics are active substances that are not primarily considered painkillers, but nevertheless have a good analgesic effect in certain forms of pain. For example, antispasmodics (anticonvulsants) are given for spasmodic or colicky pain. Tricyclic antidepressants can help with pain caused by nerve damage (neuropathic pain), which is accompanied by discomfort and often a burning sensation.
Efficient painkillers
Opioids are the most efficient painkillers in palliative care. However, pain therapy with these highly potent active ingredients carries risks: opioids can be addictive – not so much psychologically as physically (physically). There is a particular risk of dependency with strong opioids, i.e. WHO level 3 painkillers, which are therefore subject to the Narcotics Act (Germany, Switzerland) and the Narcotic Drugs Act (Austria): Their prescription and dispensing are therefore very strictly regulated.
In contrast, the weakly effective opioids of WHO level 2 (at least up to a certain dose) can be prescribed on a normal drug prescription – apart from tilidine: due to its high potential for abuse, drugs containing tilidine with a rapid release of the active ingredient (i.e. mainly drops and solutions) fall under the Narcotics Act or the Narcotic Drugs Act.
Palliative sedation
In palliative medicine, sedation is the reduction of a patient’s level of consciousness with medication (in extreme cases, even to the point of unconsciousness). It can be a side effect of pain relief with opioids or can be deliberately induced in order to spare patients unbearable pain, anxiety and other stresses in the last phase of life as far as possible. In the second case, doctors call this “palliative sedation”. In the past, the term “terminal sedation” was also used because it was feared that sedation would shorten the patient’s life. However, this is not the case, as studies have now shown.
If possible, palliative sedation should only be used with the patient’s consent and only if their symptoms cannot be alleviated in any other way.
Various groups of drugs can be used for sedation: Benzodiazepines (such as midazolam), neuroleptics (such as levomepromazine) or narcotics (anesthetics such as propofol). Palliative sedation can be continuous or intermittent, i.e. with interruptions. The latter is preferable because it has the advantage that the patient experiences periods of wakefulness in between, which makes communication possible.
Palliative care: pain therapy carefully assessed
This also applies in particular with regard to the risk of dependency (and the risk of other serious side effects) with opioids. The goal of palliative medicine is to make the last phase of life as comfortable as possible for seriously ill people. Pain therapy with opioids is sometimes the only way to achieve this goal – in consultation with the patient and their relatives.
