Pain: opioids, acetaminophen… new forms to improve their use

Acute pain: the choice of quick relief

Back pain, migraine, joint pain, inflammatory pain, post-surgical pain… 92% of people declare suffering from short (acute pain) or persistent (chronic pain: more than 3 months and resistant to treatment) pain each year. Pain is part of the French daily lives and is the first cause of medical consultation.

The World Health Organization has classified drugs for pain relief into three distinct categories.

Tier 1 analgesics are recommended to treat mild to moderate pain. The main tier 1 medications are acetaminophen, aspirin, NSAIDs (non-steroidal anti-inflammatory drugs) such as ibuprofen for example.

Tier 2 analgesics, prescribed to relieve moderate to severe pain, i.e. all pain that cannot be treated by Tier 1 pain medications, are weak opioid pain medications such as tramadol or codeine.

Tier 3 analgesics are recommended for severe pain or pain that is resistant to Tier 2 pain medications. Tier 2 medications are strong opioid pain medications: morphine and its derivatives. These drugs share the same characteristics and mechanism of action as the previous ones, but are more powerful, with greater side effects and can lead to addiction problems.

The galenic form is chosen according to the administration mode (oral, rectal, intravenous…) and influences the speed of action of the drug.

Standard release treatments are used to treat acute pain. The vast majority of them are available in the form of capsules, tablets, effervescent tablets, orodispersible or sublingual tablets.

Effervescent tablets are designed to dissolve quickly in water and release the active ingredient in the stomach in less than 15 minutes, to take effect in 30 to 45 minutes.

The orodispersible tablets, to be placed under the tongue, take between 10 and 45 seconds to dissolve in the mouth. They are best suited for people with swallowing problems or who have difficulty swallowing (elderly patients and/or patients with cognitive impairment and dementia).

Acetaminophen is also available in liquid stick-packs. This innovative galenic technology is particularly adapted to young children. Its pre-measured dose format offers a practical advantage and facilitates proper use.

These same drugs can also be presented in injectable form, which can be administered intravenously.

Chronic pain and sustained-release forms… to reduce side effects and the number of doses taken per day.

Long-acting forms of painkillers are a good alternative for chronic pain. These extended-release (ER) medications can be oral or injectable. They allow the regular and sustained action of the active ingredient over time. Dissolution and absorption of the active ingredient takes place in the intestine, releasing a constant amount of active ingredient over a longer period of time.

These forms prevent gastric irritation or the degradation of fragile active ingredients at acid pH in the stomach. They are mostly gastro-resistant forms.

Their main interest is to space the frequency of intake, especially in the case of chronic pain. 

Morphine or morphine derivatives in ER form have the advantage of reducing the number of doses taken and reducing the side effects.

Similarly, the recent introduction of tramadol hydrochloride ER has significantly improved pain management by extending the effect of the active ingredient in this pain medication. The advantage of this presentation is also that it offers very good stability and improved tolerability. This drug is increasingly used in pediatrics.

These ER forms must absolutely not be crushed to keep their prolonged effect intact. Pharmaceutical advice is required when dispensing in pharmacies! 

Patches and drugs in transdermal form

Other shape and effect with patch or transdermal device. Appeared in the 90s, it is designed to let the active substance diffuse through the skin to reach the blood vessels without passing through the digestive and hepatic system, thus avoiding the side effects of certain painkillers such as NSAIDs (non-steroidal anti-inflammatory drugs).

A large majority of pain patches contain a morphine derivative such as fentanyl, which can also be injected or taken by nasal or oral transmucosal route.

Reservoir patches contain a pouch in which the active substance is in liquid solution or in the form of a gel regularly released through a semi-permeable membrane.

In matrix patches, the active substance is dissolved or dispersed.

New generations of patches have emerged; some are based on low electric current, or ionophoresis, others on electroporation or ultrasound and micro-needles.

More recently, transdermal patches based on extracts of high-activity cannabinoids (CBD) have been developed. Since cannabinoids are absorbed by the skin, there is a regular and sustained release of all their analgesic and anti-inflammatory properties.

They are particularly useful for the relief of chronic pain in fibromyalgia and neuropathic pain in diabetic patients.

Nevertheless, the ANSM (French National Agency for the Safety of Medicines and Health Products) has warned patients and healthcare professionals about the risks of misuse, oversights and overdoses related to transdermal devices.

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