When people experience severe pain, after surgery, during cancer treatment, or from chronic conditions, ordinary painkillers like acetaminophen (paracetamol) or ibuprofen sometimes aren’t enough. That’s where opioids and adjuvant medicines come in.

These drugs can be lifesaving and improve quality of life, but they’re also powerful substances that must be used carefully because of their side effects and potential for addiction.

The Main Players: Opioids

Opioids are a class of drugs that act on the nervous system to relieve pain. They work by binding to opioid receptors in the brain and spinal cord, reducing the sensation of pain and often producing feelings of relaxation or euphoria.

Some of the most commonly used opioids include:

1. Codeine C₁₈H₂₁NO₃

Codeine is one of the milder opioids. It’s often used to treat moderate pain and is sometimes combined with other painkillers like acetaminophen. It’s also found in some prescription cough syrups because it can suppress the cough reflex.

Fun fact: Codeine is naturally found in the opium poppy, but many medical products use codeine that’s been chemically made.

2. Tramadol C₁₆H₂₅NO₂

Tramadol is a synthetic opioid, meaning it’s made in a lab. It not only binds to opioid receptors but also affects neurotransmitters like serotonin and norepinephrine, which can boost its pain-relieving effects. It’s used for moderate to moderately severe pain.

Caution: Tramadol can cause dizziness, nausea, and, in rare cases, seizures.

3. Morphine C₁₇H₁₉NO₃

Morphine is one of the strongest natural opioids and has been used for centuries. It’s the standard against which other pain medications are compared. Hospitals often give morphine through injections for severe pain, like after major surgeries.

Morphine works very effectively but can also cause drowsiness, constipation, and dependency if misused.

4. Fentanyl C₂₂H₂₈N₂O

Fentanyl is a very potent synthetic opioid, about 50 to 100 times stronger than morphine. It’s used to manage severe pain, especially in cancer patients or during surgeries.

Fentanyl is effective in tiny doses, but accidental misuse can be deadly. This is why it’s closely controlled in medical settings.

Adjuvant Medicines: The Supporting Cast

While opioids are the main pain relievers, adjuvant medicines are drugs that weren’t originally designed for pain but can enhance pain relief when used alongside opioids or sometimes on their own. Two important groups are antidepressants and anticonvulsants.

1. Antidepressants

Some antidepressants, especially tricyclic antidepressants (TCAs) and SNRIs (serotonin-norepinephrine reuptake inhibitors), can help relieve certain kinds of nerve pain (neuropathic pain), like the burning or tingling sensation caused by diabetes or shingles.

They work by increasing levels of neurotransmitters in the brain and spinal cord that help block pain signals.
Unlike opioids, they don’t provide instant relief, benefits often take a few weeks to appear.

2. Anticonvulsants

These are drugs typically used to treat epilepsy, but some, like gabapentin and pregabalin, are effective for nerve pain too.

They work by calming overactive nerve signals that cause pain.
Anticonvulsants are commonly prescribed for chronic pain conditions, especially nerve-related pain that doesn’t respond well to opioids.

Why Not Just Use Opioids Alone?

While opioids are powerful, they come with serious risks:

Tolerance: over time, the body can get used to the drug, requiring higher doses for the same effect.
Dependence and addiction: some people may develop cravings or misuse opioids, leading to substance use disorders.
Side effects: these include constipation, nausea, drowsiness, and in high doses, dangerous slowing of breathing.

Using adjuvant medicines alongside opioids can help lower the required opioid dose, reduce side effects, and target different pain pathways, making pain control more effective and safer.

The Chemistry Behind the Effect

At the chemical level, opioids work by fitting into opioid receptors like keys into locks. These receptors are part of the body’s natural pain control system, which normally responds to endorphins, the body’s natural painkillers.

When opioids bind to these receptors, they block the transmission of pain signals and trigger the release of dopamine, a “feel-good” neurotransmitter. This explains why opioids can both relieve pain and create feelings of euphoria.

Adjuvant drugs, on the other hand, alter nerve signaling in different ways, by adjusting neurotransmitter levels (antidepressants) or stabilizing nerve activity (anticonvulsants). This complementary action makes them valuable partners in pain management.

Real-World Impact

Opioids and adjuvant medicines are essential in modern medicine. They help patients recover from surgeries, manage chronic illnesses, and improve quality of life. However, misuse, especially of potent opioids like fentanyl, has led to public health crises in several countries, including widespread addiction and overdose deaths.

That’s why doctors carefully control how these medicines are prescribed and often combine them with other pain management strategies like physical therapy, psychological support, and non-opioid medications.

In Conclusion

Opioids and adjuvant medicines represent the chemistry of pain relief, a delicate balance between powerful benefits and serious risks. Understanding how they work helps us appreciate both their medical importance and the responsibility required to use them safely.

Opioids and Adjuvant Medicines