Drug dependence is a disease state in which physical dependence on a substance leads to compulsive and repetitive use despite negative consequences to the user's health, mental state or social life. Globally, UNODC (United Nations Office on Drugs and Crime ) estimates that between 155 and 250 million people, or 3.5–5.7% of the population aged 15–64, used illicit substances at least once in 2008. Among them 16–38 million became “problem drug users,” which represents 10% to 15% of all people who used drugs. Even though the consequences of the drug abuse are devastating, only 12% to 30% of “problem drug users” had received some type of treatment, which means that 11 to 34 million problem drug users (70% -88%) received no treatment at all ().1
Illicit drug use at the global level among people aged 15–64 years in 2008
Opioid dependence is considered to be a lifelong, chronic relapsing disorder and substantial therapeutic efforts are needed to keep people drug free. Methadone maintenance therapy (MMT) was introduced in 1960s, and is currently recommended for opioid dependence because its outcomes are far superior to detoxification treatment.2
However, MMT is associated with a number of problems including diversion, overdose, high attrition rates within the first month, and the high cost of the maintenance clinics needed for the daily administration.3
In comparison, buprenorphine has a lower risk of overdose than methadone, limited diversion, fewer toxic medication interactions than methadone, and much greater patient access than methadone treatment.4
However, the reports to date suggest that buprenorphine has not surpassed methadone in its effectiveness for eventual sustained abstinence.2
Both methadone (opioid agonist) and buprenorphine (a partial opioid agonist) are susceptible to diversion, abuse and overdose, and various adverse reactions such as respiratory depression and sudden death.2,4,5
Thus, agonist treatments are not optimal for all patients and most patients will need a transition to some type of antagonist treatment like naltrexone. Naltrexone is a long acting opioid antagonist that does not produce euphoria and is not addicting. It is particularly suitable to prevent a relapse to opioid use after heroin detoxification for those with substantial contingencies that will enhance their compliance with treatment.2,6
However, only weak evidence supports naltrexone's effectiveness in clinical settings despite its theoretically ideal properties.2
Overall, the programs for controlling heroin addiction are costly. For example, the United States spent approximately $21.9 billion dollars on heroin addiction in 1996 alone. High cost has made these opiate maintenance programs unfeasible in much of the world7
and parts of the United States.8
Outcomes are also relatively poor with less than 25% of heroin addicts remaining abstinent after leaving methadone maintenance treatment9
and 60% of heroin addicts lapsing within 3 months following inpatient detoxification treatment.10
Finally, some individuals who are on these programs continue to use illicit drugs, commit crime and engage in behaviors that promote the spread of communicable diseases, such as HIV/AIDS and hepatitis B and C.
Cocaine is the most problematic drug worldwide after the opiates, notably in the Americas. Government surveys indicate that 2.4 million Americans age 12 or older are current users of cocaine, and 18% of them become “problem drug users”.11
There is a clear link between cocaine use and mortality with cocaine involved in close to 40% of all drug deaths in the United States.12
Although promising lines of pharmacotherapy research are examining medications that affect dopaminergic, GABAergic, serotonergic, or glutamatergic systems, there are no pharmacotherapeutic agents currently FDA approved for cocaine addiction.
Methamphetamine use may constitute a threat to health that is similar to abuse of crack cocaine, and its abuse has grown at alarming rates in rural areas in the United States over the past two decades, as well as being widespread in Southeast and East Asia more recently.13,14
Methamphetamine is highly addictive and toxic with abuse leading to high drug accumulation in most body organs and toxicity from potent central and peripheral sympathomimetic effects. 15,16,17
This widespread and long-lasting distribution of methamphetamine parallels its long-lasting behavioral effects, and likely contributes to various medical complications associated with its abuse, underscoring both the need and the challenge in developing an effective therapies.18
Currently, there are no FDA approved medications for treating methamphetamine addiction.
Tobacco addiction, the second-leading cause of death in the world is associated with approximately 5 million deaths each year, or 1 in 10 adult deaths. Currently, there are 1.3 billion smokers worldwide, 19
and with the present smoking trends, tobacco will kill 10 million people each year by 2020.20
To date, three medications are FDA-approved for smoking cessation: nicotine replacement therapy, sustained-release bupropion, and varenicline.21,22
Despite the relative efficacy of these first-line medications, long-term abstinence rates remain disappointingly low. Even through 75% of smokers want to stop smoking, less than 5% of those who make an attempt at quitting are successful.23
In summary, we either lack treatments (cocaine and methamphetamine) or have had limited success with existing therapeutics (heroin and nicotine). These limitations in treatment have opened the opportunity for developing alternatives such as vaccines for drug abuse. Anti-addiction vaccines have distinctly different mechanisms and therapeutic utility from small molecule approaches to treatment. They do not rely on inhibiting drug binding at specific receptors within the brain; rather the antibodies serve as pharmacokinetic antagonists, favorably altering the concentration-time course of drug distribution to multiple organ systems, especially reducing drug concentrations in the brain. Furthermore, vaccine production is less expensive, thus, they have great potential to become available for wider ranges of patients world-wide and for complementing the psychosocial tools needed for a transition to a medication-free and abstinent life.