*2.7.2. Morphine*

O OH

Aspirin (1)

OCH3

HO

Thebaine (4)

N

O

344 Pain Relief - From Analgesics to Alternative Therapies

O

O

HO OH

Pawhuskin (7)

OH

**Figure 1.** Chemical structures of analgesic compounds from medicinal plants.

O

Morphine (2)

O

O O

Salvinorin A (5)

N

O

O

OH

O

O

Codeine (3)

OH

Menthol(6)

OH

<sup>O</sup> <sup>O</sup>

Cocaine (8)

O

O

OH

N

OCH3

O

O

N

OH

OCH3

An additional distinguished example is *P. somniferum*, a flowering poppy that yields opium, which contains a potent narcotic alkaloid constituent called morphine that acts as an opioid receptor [52]. Morphine binds to opioid receptors; molecular signaling activates the receptors to mediate certain actions. μ (Mu) receptors exist in the brain stem as well as in thalamus activation, these receptors result in relief of pain and sedation. Kappa receptor is found in the limbic system, part of forebrain, spinal cord, and brain stem. Activation these receptors result in relief of pain and sedation. Delta receptor found in brain, spinal cord, and digestive tract, stimulation of delta receptor leads to analgesic.

## *2.7.3. Ziconotide*

Ziconotide, also known as SNX‐111, is a novel nonopioid analgesic drug. It is a synthetic version of ω‐conotoxin MVIIA (ω‐MVIIA), which is a peptide that is found in the venom of the fish‐eating marine snail, *Conus magus*. It is a powerful analgesic drug that acts through a mechanism that involves selective block of N‐type calcium channels. This action inhibits the discharge of pronociceptive neurochemicals such as glutamate, calcitonin gene‐con‐ nected peptide, and material P in the brain and spinal cord, ensuing in pain relief. It has been approved for the treatment of severe chronic pain in patients only when administered by the intrathecal route. Importantly, prolonged administration of ziconotide does not lead to the development of addiction or tolerance [53].
