Minimum of unpleasant sensations and a fast analgesic effect are the two main criteria for choosing pain relievers. The main tasks of all painkillers are easing the pain and changing the emotional state from negative to neutral.
Safe and effective pain relievers should have the following characteristics:
- fast start action onset;
- low systemic toxicity and minimal risk of side effects;
- adequate duration of pain relief, which should be at least 4 hours.
Analgesic effect is achieved by selecting pain relievers individually for each patient. There is no single dose or drug, which would be multi-purpose and would alleviate physical and emotional discomfort for all patients. In addition, for a variety of reasons (progression of the underlying disease, development of tolerance, etc.), previously used drugs may become ineffective for pain alleviation in repeated use.
As a rule, there are three dosage forms of pain relievers:
- pills
- injections
- topical products
All drugs for facilitating physical and emotional sufferings should be used in the simplest, most effective and least painful way. Therefore, to ease the painful and unpleasant sensations, many patients prefer to use tablets because of the convenience and ease of their use.
Tablets for pain relief can be either of immediate or of sustained release of the drug substance. Pain relievers with an immediate release are used to relieve episodic and breakthrough pain (BTP).
Extended release tablets are used to alleviate chronic pain and provide a longer analgesic effect, than that of conventional tablets. Thus, using prolonged release tablets, patient can reduce the frequency of medication.
The main disadvantages of oral pain relievers are:
- insufficiently rapid onset of the analgesic effect, compared to injectable preparations;
- most of the drug substance is inactivated upon first passage through the liver;
- impossibility to select the dosage necessary for adequate analgesic therapy with absolute accuracy.
Injectable pain relievers are first line drugs to alleviate physical and emotional suffering in outpatient practice. Parenteral administration of pain medication is necessary for fragile patients, who are unable to swallow tablets.
Injectable pain relievers should also be used by patients, who:
- suffer from a gastrointestinal tract dysfunction
- require very rapid onset of the analgesic effect
- are incapable of using or tolerating the action of oral analgesics
The main advantage of injectable analgesics vs oral analgesics is the speed of action, since the drug substance is not absorbed from the gastrointestinal tract, and immediately enters the blood stream.
In outpatient practice, injectable drugs can serve not only for analgesia (loss of pain sensation), but also for anesthesia (loss of pain sensation, as well as motor activity and consciousness). Clinical efficacy of injectable pain relievers is determined by such indicators, as:
- duration of anesthesia for therapeutic purposes;
- active profile, that is, the duration of complete and incomplete anesthesia;
- the onset of action, that is, the time to achieve an analgesic effect after injection;
- the total duration of anesthesia, that is, until the sensitivity returns completely.
Of the parenteral ways of pain relievers administration, the subcutaneous way is the main one, while the intravenous way is used in need to quickly alleviate emotional and physical suffering. Intramuscular administration of drugs is only used for strict medical indications and mainly to alleviate severe pain.
Pain relievers of topical application can be ointments, creams, sprays and patches. Local analgesics should be used for symptomatic treatment of sore throat, as well as painful and unpleasant sensations, caused by injuries, bruises and sprains.
The effectiveness of the analgesic effect of topical drugs is the direct impact on the source of pain and inflammation. Other advantages of pain relievers for topical application vs oral and injectable medications:
- no adverse effects on the liver and gastrointestinal tract;
- decrease in the risk of side effects due to low systemic bioavailability of the drug;
- ease of use, the possibility of using at home, the lack of the need for outpatient treatment.
The drawbacks of pain relievers for topical application that should be noted are inefficiency against chronic pain, the inability to achieve an immediate analgesic effect and an increased risk of allergic reactions on the skin.
By its effect on the body, all pain relievers are divided into two large groups: narcotic and non-narcotic. The former have a pronounced stimulating effect on the brain and the central nervous system. Non-narcotic drugs suppress the activity of pain mediators.
The action mechanism of opioid pain relievers lies in:
- violation of the subthreshold pain impulses functioning
- change in emotional perception of painful and unpleasant sensations
- blocking the interneuronal transmission of pain impulses to the cerebral cortex
Narcotic analgesics can be agonists or antagonists of opiate receptors, which are responsible for the severity and degree of pain intensity. The therapeutic effect of opioid pain relievers is combined with the impact over patient’s emotions and psychological condition. The main advantages of narcotic drugs are the fast and long-term elimination of symptoms of acute and chronic pain.
Non-narcotic analgesics, posses anti-inflammatory and antipyretic effects in addition to the analgesic effect. The action mechanism of non-narcotic pain relievers lies in:
- blockage in the development of pain mediators in the peripheral nervous system
- inhibition of painful impulses transmission along the peripheral nerves and into the deeper parts of the brain
Unlike opioid analgesics, which can be addictive, non-narcotic drugs do not contribute to drug dependence.