In the management of chronic pain, the drug to be used as per first WHO ladder-step is:
**Core Concept**
The World Health Organization (WHO) pain ladder is a three-step approach to pain management, which recommends increasing the intensity of analgesia based on the severity of pain. The first step focuses on non-opioid analgesics for mild to moderate pain.
**Why the Correct Answer is Right**
The first step of the WHO pain ladder involves the use of non-opioid analgesics, such as acetaminophen (paracetamol) or NSAIDs (non-steroidal anti-inflammatory drugs), to manage mild to moderate pain. These medications work by inhibiting the production of pro-inflammatory mediators, such as prostaglandins, and by blocking the action of pain signals in the central nervous system. The correct answer, **Tramadol**, is a weak μ-opioid receptor agonist and a serotonin-norepinephrine reuptake inhibitor, which can also be used in the first step of the WHO pain ladder for mild to moderate pain.
**Why Each Wrong Option is Incorrect**
* **Option A:** **Codeine** is an opioid analgesic, which is typically used in the second step of the WHO pain ladder for moderate to severe pain.
* **Option B:** **Fentanyl** is a potent opioid analgesic, which is usually reserved for severe pain in the third step of the WHO pain ladder.
* **Option D:** **Morphine** is a strong opioid analgesic, which is typically used in the third step of the WHO pain ladder for severe pain.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that the WHO pain ladder is a stepwise approach, and the choice of analgesic should be based on the severity of pain, rather than the type of pain. Non-opioid analgesics should be used as the first-line treatment for mild to moderate pain.
**Correct Answer:** C. Tramadol.