Pain killers

Clinical Pharmacology of Opioid Analgesics

What is pain relief?

Pain relief is an essential element of medical practice and requires careful selection of the type of medication, selection of the required dose and constant objective assessment of the underlying disease. There are many situations in which analgesia is needed before a definitive diagnosis is made.

In acute situations, the elimination of pain facilitates the collection of anamnesis, physical examination, which speeds up the specification of the diagnosis. The use of opioids in acute situations is different from their use in the treatment of chronic pain, in which it is necessary to take into account such factors as tolerance (a complete or partial reduction in the analgesic effect) and physical dependence.

In order to obtain adequate analgesia, a selection of medications is necessary that are appropriate to the nature and intensity of the pain. The severity of pain syndrome is not the same in different diseases. Each anesthetic drug has a therapeutic “ceiling,” and an attempt to raise this “ceiling” by increasing the dose carries the risk of significant adverse reactions.

Analgesia

Severe persistent pain usually subsides when prescribing more effective and powerful opioids, while acute short-term pain is not so adequately suppressed by them. An attempt should be made to quantify the pain, and this information should be used to select the appropriate drug and control its action.

In the process of choosing a drug, sound routes of administration (orally or parenterally), the intended duration of treatment, information on the use of opioids in the past are of particular importance.

Pain associated with cancer or other terminal conditions can and should be adequately eliminated, and concerns about tolerance and dependence should be set aside in order to achieve the goal of maximum relief for the patient.

Developed adverse reactions in the form of drowsiness, difficulty in contact, orientation indicate the need to reduce the dose. If the patient sleeps well at night, there is no need to wake him up for the next dose, and later it is better to use a double dose of tram before bedtime.

The rectal route of administration is characterized by uneven absorption, which depends on the depth of injection of the suppository, body temperature (the degree of vasoconstriction), and the presence of feces in the rectum, so it is recommended to use suppositories in addition to oral or parenteral administration.

Tramal refers to analgesics of moderate strength. Its analgesic effect has a unique dual mechanism of action. Part of the tramadol molecules activates the analgesic mu-opioid receptors. At the same time, the affinity of tramadol to these receptors is 6 thousand times weaker than that of morphine; therefore, the narcogenic potential of this drug is very weak. The second part of tramadol molecules simultaneously activates non-opioid analgesic systems – inhibits the reuptake of serotonin or norepinephrine in nerve synapses. Due to the activation of non-opioid noradrenergic and serotonergic systems, tramadol inhibits the transmission of pain impulses at the spinal level. The contribution of each mechanism of action separately is rather weak, but in general, there is a multiple enhancement of general analgesia. It is the synergism of the two mechanisms of action of tramadol that makes it highly effective. The low affinity of tramadol to opioid receptors explains the fact that at the recommended therapeutic doses tramadol does not cause respiratory depression and blood circulation, impaired gastrointestinal motility (constipation) and urinary tract, with long-term use does not lead to the development of drug dependence.

Tramadol is presented in non-invasive forms: capsules – 50 mg, drops (20 drops – 50 mg), suppositories – 100 mg, long-acting tablets (100, 150 and 200 mg), there are also ampoules of 50 and 100 mg. When ingestion tramadol is characterized by high bioavailability, which is very important with long-term treatment of chronic pain syndrome. When taken orally, tramadol is rapidly and 90% absorbed in the gastrointestinal tract, the maximum concentration in the blood is reached 2 hours after taking the capsules or drops. The initial dose of tramadol is 50 mg, daily doses of tramadol range from 50 to 400 mg.

Titration of the dose for 2-3 days helps to avoid adverse events. For the selection of the dose most convenient drops. It is recommended to assign 10 drops to the 1st intake, 20 drops (or 1 capsule each) for the 2nd and 3rd doses. On the first day of treatment with tramadol, the daily dose should be about 100 mg, from the second day, 50 mg capsules can be administered 3-4 times a day, and from the third day, the dose needed for adequate pain relief. The daily dose should not exceed 400 mg.