Preface

Over the past two decades, some countries have observed an increase in the use of opioid drugs for pain management, including non-oncological pain. The use of prescription opioids is sometimes justified to decrease or abolish the nociceptive sensation but the misuse of this kind of drug, the rise in heroin consumption, and the escalation in the abuse of high-potency synthetic opioids, such as fentanyl, have led to the declaration of an opioid epidemic.

Nowadays, morphine and other opioid drugs are widely used for pain relief in many conditions but their use is associated with potential complications. For example, opioids can produce a rebound effect and cause more pain instead of relief and they have a high chance of generating tolerance, dependence, and addiction, a brain disease induced by repeated or chronic use of these drugs that causes adaptive or allostatic changes (i.e. cellular or system adaptations) that modify the neuronal circuitry, inducing a "drug-dependent" state. This state persists even after drug consumption and affects the feeling of well-being, learning, stress, decision-making, and self-control.

This book is written by international scientists with expertise in psychobiology, addiction, and pain management, and addresses different aspects of opioids, such as understanding central pain and central sensitization for better patient care, effectiveness of morphine in other conditions apart from pain control, neurobiological mechanisms associated with opioid addiction, and pharmacological treatments for this disease.

With this book culminates an intense project in which I would first like to highlight the involvement of all authors who have contributed to a text of great quality and scientific rigor. I would like to thank Ms Romina Rovan, Ms Rozmari Marijan and Ms Manuela Gabric, the Author Service Managers for this book at IntechOpen, for their assistance during book preparation. Finally, I would also like to dedicate this book to my mentor, Professor María Luisa Laorden, and to my family, without any of them, it would not have been possible to get here.

### **Pilar Almela Rojo**

Associate Professor, Department of Pharmacology, Faculty of Medicine, University of Murcia, Spain

**1**

Section 1

General Considerations

Section 1
