Substance Abuse & HIV/AIDS

Substance Abuse & HIV/AIDS

The Correlation, Risks & Causes

substance abuse and hiv

Substance abuse is the excessive use of a substance, such as drugs or alcohol, which results in clinical and functional impairments.

This loss of function can include detriments to professional, academic, and social interactions 1. Ongoing substance abuse can cause severe health problems over time, even in previously healthy individuals. These health complications include increased disease risk, difficulty in detecting and diagnosing certain disease states, a reduced inherent ability to recover from certain diseases, and a decrease in the effectiveness of various treatments.

With regard to HIV and AIDS, substance abuse plays a significant factor in infection and disease progression. Although HIV/AIDS can affect anyone, the risk of infection is significantly higher in patients suffering from substance abuse, whether the risk is of direct exposure through needles or increased likelihood of high risk behavior due to loss of judgment. Substance abuse is of primary concern to HIV/AIDS by promoting actions which increase the initial risk of infection. Furthermore, some abused substances can also influence disease progression and interfere with the effectiveness of treatment.

Pathology of HIV/AIDS

cd4 t-cells and hiv

HIV (human immunodeficiency virus) is a virus that is transmitted in bodily fluids, often by sharing a used needle or having sexual intercourse with an infected individual.

When a person becomes exposed to HIV, the virus infects the patient’s white blood cells, particularly CD4+ T cells 2.

These T cells are crucial players in a healthy body’s ability to mount an appropriate immune response to infections – their loss results in markedly diminished immune functioning.

Within a few weeks, the infected cells are either destroyed by the virus or by the immune system itself. The loss of these cells characterizes the acute phase of the infection. During this phase, the virus is rapidly replicating and the patient is able to infect other people from their time of infection onward. Within the first month or two following exposure and infection, patients experience swollen lymph nodes and flu-like symptoms including fevers, aches, and joint pain.

After this time, the disease enters the chronic stage of HIV infection which may last for several years. With effective treatment this stage can be extended to several decades in some patients. During this stage, the virus continues to replicate and stimulate an immune response. This chronic response may be due in part to an increased, system-wide bacterial load resulting from the decreased vigilance of a weakened immune system 3. The immune system actively attempts to replenish the lost T cells, which also subsequently become infected by the virus. This chronic immune and T cell activation causes additional strain on the immune system as the body loses the ability to maintain a sufficient supply of T cells.

The heightened activation of T cells can be used as a predictor for disease progression toward AIDS 4. Once there are no longer enough T cells to mount an immune response, a patient crosses below an immunological threshold and is considered to have developed acquired immunodeficiency syndrome (AIDS). Because of the association of the virus (HIV) with the late stage disease (AIDS), this guide will refer to the virus itself as HIV and to the whole disease as HIV/AIDS.

Health problems caused by untreated HIV/AIDS

It often takes several years for a person infected with HIV to develop full-blown AIDS. During this time, treatment options are available that can delay or stop the disease progression for many years. There is no cure for HIV, so an infected individual will always have the virus, even if they are undergoing treatment. Despite the lack of a cure, a patient can still maintain a high quality of life as long as the disease is managed with medication. Currently, combined antiretroviral therapies (referred to as ART, or HAART for highly active antiretroviral therapy) exist for the treatment of HIV. These therapies are able to dramatically slow viral replication and disease progression, thus delaying the onset of AIDS. For some patients, this treatment can delay disease progression for several decades. The current ability to effectively stop the development of AIDS in HIV-positive individuals makes effective adherence to medications and avoidance of complicating factors, such as substance abuse, critical to maintaining a high quality of life.

Because HIV infection reduces immune function, many other types of infections are an ongoing concern for HIV/AIDS patients. In particular, viral hepatitis is a concern because of the similar modes of transmission and prevalence of each disease within the same populations 5.

toxoplasmosis risk

The diminished immune function puts HIV/AIDS patients at a greater risk of infection with many opportunistic diseases that would not otherwise affect a healthy individual. HIV/AIDS also places these patients at a higher risk of increased disease severity when they are exposed to any illness. The risk of these additional infections varies by the individual and where they live. For example, HIV/AIDS patients in poor nations face an increased risk of tuberculosis (TB), making TB a leading cause of death for HIV/AIDS patients in those areas 6. TB is generally not considered to be a major problem in most developed countries, but HIV/AIDS patients are highly susceptible to infection. Patients who care for cats and come in contact with cat litter or cat feces face an increased risk of toxoplasmosis. Toxoplasma gondii is a common protozoan parasite, and many healthy people are exposed to it regularly. Although exposure to Toxoplasma normally only results in a mild reaction, it can be harmful to pregnant women and it can be fatal to individuals with weakened immune systems 7.


HIV/AIDS patients also have an increased risk of several cancers.

lung cancer

In some cases these cancer risks are due to other factors commonly associated with HIV/AIDS. For example, smoking is more common among HIV/AIDS patients, and the increased smoking rate among HIV/AIDS patients may account for much of the increased incidence of lung cancer among that population. However, other cancers appear to be more common as a result of HIV infection and disease progression. Because HIV primarily targets immune cells, HIV/AIDS can lead to lymphoma, which is a cancer of the white blood cells. Another cancer common in HIV/AIDS patients and rare in uninfected people is Kaposi’s sarcoma. This cancer affects blood vessels and causes the characteristic reddish lesions that have often been associated with AIDS patients. Other cancers, including Hodgkin disease and testicular seminoma also appear to occur at a higher frequency in HIV/AIDS patients as a result of decreased immune function 8.

Other complications experienced in a conjunction with HIV/AIDS include severe weight loss and kidney disease. The weight loss experienced in AIDS patients is referred to as wasting syndrome and is marked by a greater than ten percent loss of body weight. This weight loss is often attributed to a loss of muscle mass and may be associated with diarrhea and extreme weakness. Kidney disease associated with HIV infection is referred to as HIV-associated nephropathy. This form of kidney disease is characterized by glomerular lesions in the kidneys. Prior to the introduction of antiretroviral therapies, HIV-associated nephropathy often led to kidney failure and the need for life-sustaining dialysis.


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Substance abuse increases the risk of HIV/AIDS

Substance abuse can indirectly and directly increase the risk of contracting HIV/AIDS. For instance, ten percent or more of HIV cases annually can be attributed to injection drugs.
abuse and increased hiv risk

Indirect risks are changes in behavior that increase the chance that someone would be exposed to the virus. The abuse of alcohol and other non-injection drugs is associated with an increased risk of HIV infection 9. Many drugs, including alcohol, reduce inhibitions and impair judgment. As a result, alcohol may make risky behavior more likely, such as unprotected sex and sex with multiple partners. In cases such as this, the use of alcohol is not directly related to HIV/AIDS risk, but the actions as a result of substance abuse can lead to increased risk. This is true for nearly all substance abuse. Anything that impairs judgment also increases risk.

Direct risks of HIV exposure occur in the form of contaminated needles and drug injection supplies. When needles are shared among users, traces of blood may be transferred between individuals as well. Even when a clean needle is used, such as the ones obtained through needle-exchange programs, any other materials used for the injection may also contain blood or body fluids. For example, solutions used to dissolve drugs or cotton balls that have come in contact with the needles can easily become contaminated between users. Even in the case of injection drugs, sexual practices while under the influence are a common route of HIV infection 10.

The negative impact of alcohol abuse on HIV/AIDS

In addition to increasing the risk of exposure to HIV, alcohol abuse can also negatively affect HIV/AIDS treatment and maintenance in many ways. Chronic alcohol abuse weakens the immune system.

whiskey

This is extremely important for HIV/AIDS patients because their immune systems are already weakened by the disease. Further weakening the immune system increases the risk of additional infections while also raising the chance that HIV replication may increase. Even with proper medication, such as antiretroviral therapy (ART), maintaining the best immune function possible is important to preventing disease progression. HIV patients who are heavy drinkers have diminished effectiveness of antiretroviral therapies. Specifically, heavy drinkers are two to four times less likely to achieve a positive response while undergoing antiretroviral therapies 11.


Alcohol can also be detrimental to HIV patients due to its ability to decrease awareness and inhibit judgment.

HIV patients are required to take a very strict regimen of medications in order to treat HIV and prevent its progression to AIDS. Anything that impairs a patient’s ability to take the correct amount of medications at the correct times can have a negative impact on disease treatment.

Alcohol damages the liver

alcohol, hiv and liver damage

Excessive alcohol consumption can lead to liver damage, cirrhosis, and eventually culminate in end stage liver failure. Because of the liver damage associated with ethanol consumption, alcohol is particularly problematic for other conditions that also affect the liver. This is the case for HIV/AIDS patients, given the hepatic consequences of HIV itself combined with the impact that HIV/AIDS pharmaceutical treatment can have on the liver.

As mentioned, many HIV/AIDS patients also suffer from other infections that affect the liver, such as hepatitis 12. HIV infection can exacerbate the liver damage caused by these other diseases. Many drugs used to treat HIV, such as antiretroviral drugs, carry a risk of liver toxicity. Because treatment of HIV takes priority over many other medical issues, patients will often receive treatment even in the presence of prior liver damage. Because it is so important to continue to treat HIV infection, it is also important to minimize any additional risks of liver damage.

Drug use and HIV/AIDS

Alcohol is not the only substance that can be abused. Any chemical that changes the way the mind or body functions is defined as a drug. Substance abuse includes the use of illicit drugs, such as the misuse of prescription drugs or the use of recreational or illegal drugs. Drugs that have not been approved by a physician for medical use are characterized as recreational or illegal drugs. This text focuses on the drugs that are used by people with HIV and AIDS and how those drugs can negatively impact their health and prognosis.


Different drugs have different effects depending on the individual, with many well document negative health consequences for the general population. It follows that drug use can have detrimental effects on HIV/AIDS patients. These effects range from increased risk of contracting HIV, as described above, to decreased effectiveness of medications and treatment.


Drug use may also cause problems of its own which serve to compound the problems faced by patients with HIV/AIDS. HIV/AIDS takes a toll on patients both physically and mentally, and adding addiction, depression, or risk of overdose to those problems makes it increasingly difficult for patients to maintain good health. Understanding these difficulties and complications is important in reducing risks and improving outcomes for individuals with HIV/AIDS.

The effects of smoking on HIV/AIDS

young man smoking

The rate of smoking is two to three times higher in HIV-positive adults than in the general population. This is of significant concern for HIV/AIDS patients due to the increased risk of various diseases related to smoking, and how that risk is affected by being HIV-positive.

Because HIV weakens the immune system, HIV/AIDS patients who smoke have an increased risk of mouth, throat, and lung infections. In particular, HIV/AIDS sufferers who smoke are more likely to contract pneumonia, such as bacterial or Pneumocystis carinii pneumonia (of note, this particular pneumonia is commonly abbreviated as ‘PCP’; not to be confused with the dissociative drug phencyclidine) 13. Furthermore, HIV/AIDS patients who contract this illness are far more likely to require hospitalization for treatment. Pneumocystis is an opportunistic pathogen that does not normally cause disease but, in immunocompromised individuals and HIV/AIDS patients, it can lead to a potentially life-threatening infection. Other diseases of the respiratory tract include a candidal, or yeast infection of the mouth referred to as thrush or leukoplakia 14, which is characterized by white sores in the mouth. Smoking can potentially produce an oral environment even more conducive to the development of these lesions.

effects of smoking and hiv

Other debilitating and potentially life-threatening diseases which disproportionately affect HIV-positive smokers include heart disease, stroke, cancer, and chronic obstructive pulmonary disease (COPD). HIV and HIV treatment also increases the risks of some of certain conditions that are associated with smoking, such as osteoporosis, stroke, and heart attacks 15. While smoking or HIV/AIDS alone may lead to many of these conditions, HIV/AIDS patients have a greater risk of these conditions if they smoke, further diminishing quality of life.

The effects of illicit drugs on HIV/AIDS

As mentioned above, illicit drug use affects HIV risk, HIV/AIDS complications, HIV/AIDS treatment efficacy, and long-term HIV/AIDS prognosis. Illicit drug users have increased risk of contracting HIV through the use of used needles, shared injection supplies, contaminated injection drugs, and reduced judgment leading to a heightened chance of high risk behavior.


user of illicit drugs

For illicit drug users who have HIV/AIDS, the complications due to the illicit drugs and the conditions associated with their use lead to poor treatment. Illicit drug users with HIV are less likely to have access to effective treatment options. This lack of treatment options comes in the form of relatively few accommodating rehabilitation services to address the illicit drug use as well as limited access to clinics and antiretroviral therapies to treat their HIV.

Along with the increased risk of contracting HIV, the impaired judgment and mental effects of illicit

drugs also create difficulties in maintaining a consistent HIV/AIDS treatment. Antiretroviral therapies must be maintained in order to keep the viral load low and reduce the likelihood of serious consequences and development of AIDS. Illicit drug use creates a barrier to consistent management of HIV, causing skipped treatments, incorrect dosages, and overall reduced effectiveness of treatment. Seeking treatment for the illicit drug use to reduce these complications is important in maintaining effective treatment of HIV/AIDS.

Commonly taken illicit drugs

amyl nitrate, stimulant, marijuana

Many illicit drugs are associated with HIV infection and AIDS by being commonly found within the same populations. Due to the risk of being exposed to HIV by drug injection, all injection drugs can be linked to directly to HIV/AIDS. Non-injection drugs are more likely to be associated HIV transmission by increasing the likelihood of risky behavior such as unprotected sex or sex with multiple partners. Illicit drugs also reduce the effectiveness of HIV/AIDS treatment by interfering with the ability of a patient to seek treatment and taking focus and attention off of maintaining a successful treatment regimen.

Injection drugs most commonly associated with HIV/AIDS include heroin, a depressant opioid, and cocaine, a stimulant. Various forms of amphetamine can also be abused via an intravenous route of administration. Although these are associated with HIV risk, these drugs are all floridly addictive and, without addiction treatment, it is likely that drug use of this type will continue throughout any possible HIV/AIDS treatment. It is not known whether any of these drugs directly interfere with antiretroviral therapies.

Marijuana, other stimulants, and street or club drugs (e.g., ketamine, methamphetamine, amyl nitrate) are strongly associated with sexual transmission of HIV. This is particularly true of amphetamine and amyl nitrate (poppers) which may be used to enhance sexual pleasure. As with other illicit drugs, anything that decreases the adherence to therapy for HIV/AIDS patients decrease the effectiveness of treatment and ultimately diminishes quality of life.

Illicit drugs and HIV/AIDS risk

Injection drugs are the second leading cause of HIV infection, preceded only by unprotected sex. Both of these risk factors can be attributed to illicit drug use including heroin, cocaine, stimulants and other drugs. These risks disproportionately affect certain populations. For example, illicit drug use is more common in people living in poverty, people suffering from mental illness, and abuse survivors. Gay men are also at an increased risk of illicit drug use, potentially due to the heightened risk of discrimination and mental health issues.

injection drugs
The most obvious risk of HIV associated with illicit drug use is from the sharing of needles. Although needle exchange programs can be helpful, and exist to encourage the use of clean needles among injection drug users, drugs such as heroin and methamphetamine continue to be abused via non-sterile injection, promoting the transmission of HIV among users who share used needles.

Illicit drugs and treatment of HIV/AIDS

therapy treatment schedule

As mentioned above, illicit drug use can interfere with treatment of HIV/AIDS. Although illicit drugs may not interact directly with many antiretroviral treatments, the use of illicit drugs can interfere with treatment schedules.


Illicit drug use can disrupt daily activities, potentially interfering with adherence to treatment programs. Illicit drug use also increases the risk of depression and mental illness. For patients in recovery from illicit drug use, a relapse episode can bring back all of the risks associated with illicit drug use. These factors also play a role in treatment in that a physician needs to recognize these additional factors in order to ensure that all of the patient’s physical and mental health needs are being met.

The legal consequences of illegal drug use may also pose a barrier to treatment of HIV/AIDS. Individuals who are concerned about possible punishments for illegal drugs are less likely to come forward for treatment. This fear of stepping forward decreases the likelihood of a person seeking treatment and increases the chances that HIV may be passed to other people. This environment creates a cycle where people are more likely to engage in risky behavior as a result of their drug use and they are more likely to remain in their environment out of a fear of punishment. Furthermore, some medical providers are more reluctant to provide equal services to someone who is actively abusing illicit drugs since it is unlikely that the patient will be able to adhere to an effective and successful treatment regimen.


In some cases, the use of illicit drugs or the medications used for recovery from illicit drug use may increase the risk of side effects from antiretroviral therapies. The medications used to aid recovery from addition to illicit drugs do not typically interfere with the efficacy of HIV/AIDS treatments.


methadone dose

Methadone is a common treatment option for opioid addiction. It is safe for use with antiretroviral therapies, although there are slight interactions. In particular, antiretroviral medications may lead to a decrease therapeutic methadone levels in patients. For this reason, these patients may require higher doses of methadone for effective treatment.

The good news is that HIV therapies are effective in drug users. Substance abuse can lead to an increased risk of HIV exposure, reduce an individual’s ability to get treatment and follow a treatment schedule, and lead to potential complications. However, despite these issues, HIV medications can remain effective in drug users. Illicit drug use should not pose a barrier to HIV/AIDS treatment. Furthermore, the knowledge of existing drug use shouldn’t prompt negative clinician bias against treatment.

Methamphetamine

meth and cognitive decline

Methamphetamine use is associated with risk of HIV infection, but it can also exacerbate symptoms associated with HIV/AIDS. Methamphetamine and HIV/AIDS both carry risks of neurological symptoms, and these symptoms are compounded in HIV-positive patients who abuse methamphetamines. A study examined the cognitive impairment among control patients, HIV-positive individuals, methamphetamine users, and HIV-positive methamphetamine users 16. This study found that either methamphetamine or HIV caused cognitive impairment when compared to the control group, but the cognitive impairment was significantly worse in the HIV-positive methamphetamine users. This indicates that the use of methamphetamines may accelerate the cognitive decline associated with HIV infection.

Cocaine

Cocaine use has been shown to accelerate HIV disease progression 17.

t-cells and cocaine

An active HIV infection is often measured by the number of active viral particles. Even in cases where the viral load is equal between cocaine users and control patients, the CD4 T cell population was reduced in the cocaine users 18. While adherence to treatment is always a concern in the context of illicit drug use, adherence to antiretroviral therapy is not sufficient to manage HIV in the context of cocaine use. These studies indicate that treatment for substance abuse is a necessary part of an effective HIV treatment program.

Seek professional treatment for substance abuse

Substance abuse is associated with increased risk of contracting HIV and a reduced effectiveness of HIV/AIDS treatment. In many cases, substance abuse is a causal factor for HIV infection. For some illicit drugs, including methamphetamine and cocaine, drug use can have adverse consequences on HIV and other disease progression. Illicit drug users are at increased risk of contracting HIV through unprotected sex or through shared supplies for injection drugs. Complications range from pulmonary infections in smokers to lapses in medications for illicit drug users.

emergency room

Several effective treatments for substance abuse exist. Many of these treatments can be given alongside antiretroviral therapies for the treatment of HIV/AIDS. Even without the complications of HIV/AIDS, substance abuse is a leading cause of death and emergency room visits 19. Effective substance abuse programs and treatments make this a preventable illness with multiple treatment options available.

Ongoing substance abuse can lead to organ damage 20, exacerbating the damage caused by HIV/AIDS. In some cases, the damage can also lead to increased risk of various infections or cancers, which are particularly dangerous for HIV/AIDS patients.

Termination of substance abuse can be a painful and debilitating process. For patients suffering from other diseases, such as HIV/AIDS, the process can be even more difficult. It is important to seek treatment immediately to reduce the associated risks and to receive help in controlling substance abuse. Although various medications can help the process and reduce cravings, withdrawal from illicit drugs or alcohol can lead to intense cravings, fever, sweating, nausea, vomiting, and pain throughout the body. For some types of substance abuse—including that of alcohol and benzodiazepines—the process

of withdrawal can be quite severe and, even, life threatening. With medically supervised or medically assisted addiction treatment, the early stages can be managed at a care facility, where physicians can monitor a patient’s progress and help manage their withdrawal symptoms. Getting help through the withdrawal process can make the process easier and also lead to additional opportunities for long-term mental health care to reduce the risk of relapse.

Substance abuse and HIV/AIDS are very difficult and complex diseases. The combination of these factors can increase risks of many dangerous infections and cancers and can complicate treatment options. Each condition requires intensive treatments in order to properly manage them, and the association of substance abuse with HIV/AIDS makes those treatments that much more difficult. Effective treatment of substance abuse is critical in all individuals and can lead to an improved quality of life. For anyone suffering from either of these conditions, the best option is too seek out qualified medical care and effective professional substance abuse treatment.

References

  1. American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders: DSM-IV. 4th ed. Washington DC: Author; 2000.
  2. Douek DC, Brenchley JM, Betts, MR, Ambrozak DR, Hill BJ, Okamoto Y, Casazza JP, Kuruppu J, Kuntsman K, Wolinsky S, Grossman Z, Dybul M, Oxenius A, Price DA, Connors M, Koup RA. HIV preferentially infects HIV-specific CD4+ T cells. Nature. 2002; 417:95-98.
  3. Brenchley JM, Price DA, Schacker TW, Asher TE, Silvestri G, Rao S, Kazzaz Z, Bornstein E, Lambotte O, Altmann D, Blazar BR, Rodriguez B, Teixeira-Johnson L, Landay A, Martin JN, Hecht FM, Picker LJ, Lederman MM, Deeks SG, Douek DC. Microbial translocation is a cause of systemic immune activation in chronic HIV infection. Nature. 2006; 12:1365-1371.
  4. Hazenberg MD, Otto SA, van Benthem BHB, Roos MThL, Coutinho RA, Lange JMA, Hamann D, Prins M, Miedema F. Persistent immune activation in HIV-1 infection is associated with progression to AIDS. AIDS. 2003; 17(13)1881-1888.
  5. Sulkowski MS. Viral hepatitis and HIV coinfection. Journal of Hepatology. 2008; 48(2)353-367.
  6. Narain JP, Lo YR. Epidemiology of HIV-TB in Asia. The Indian Journal of Medical Research. 2004; 120(4):277-289.
  7. Luft BJ, Chua A. Central nervous system toxoplasmosis in HIV pathogenesis, diagnosis, and therapy. Current Infectious Disease Reports. 2000; 2(4):358-362.
  8. Frisch M, Biggar RJ, Engels EA, Goedert JJ. Association of Cancer With AIDS-Related Immunosuppression in Adults. JAMA. 2001; 285(13)1736-1745.
  9. Van Tieu H, Koblin BA. HIV, alcohol, and noninjection drug use. Current Opinion in HIV & AIDS. 2009; 4(4):314-318.
  10. Doherty MC, Garfein RS, Monterroso E, Brown D, Vlahov D. Correlates of HIV infection among young adult short-term injection drug users. AIDS. 2000; 14(6):717-726.
  11. Jose Miguez M, Shor-Posner G, Morales G, Rodriguez A, Burbano X. HIV Treatment in drug abusers: impact of alcohol use. Addiction Biology. 2003; 8:33-37.
  12. Salmon-Ceron D, Lewden C, Morlat P, Bévilacqua S, Jougla E, Bonnet F, Héripret L, Costagliola D, Mayd T, Chêne G. Liver disease as a major cause of death among HIV infected patients: role of hepatitis C and B viruses and alcohol. Journal of Hepatology. 2005; 42(6):799-805.
  13. Jose Miguez-Burbanoa M, Ashkin D, Rodriguez A, Duncan R, Pitchenik A, Quintero N, Flores M, Shor-Posner G. Increased risk of Pneumocystis carinii and community-acquired pneumonia with tobacco use in HIV disease. International Journal of Infectious Diseases. 2005; 9(4):208-217.
  14. Palacio H, Hilton JF, Canchola A, Greenspan D. Effect of Cigarette Smoking on HIV-Related Oral Lesions. Journal of Acquired Immune Deficiency Syndromes & Human Retrovirology. 1997; 14(4):338-342.
  15. Lifson AR, Neuhaus J, Ramon Arribas J, van den Berg-Wolf M, Labriola AM, Read TRH. Smoking-Related Health Risks Among Persons With HIV in the Strategies for Management of Antiretroviral Therapy Clinical Trial. American Journal of Public Health. 2010; 100(10):1896-1903.
  16. Rippeth JD, Heaton RK, Carey CL, Marcotte TD, Moore DJ, Gonzalez R, Wolfson T, Grant I, The HNRC Group. Methamphetamine dependence increases risk of neuropsychological impairment in HIV infected persons. Journal of the International Neuropsychological 2004; 10(01):1-14.
  17. Baum MK, Rafie C, Lai S, Sales S, Page B, Campa A. Crack-Cocaine Use Accelerates HIV Disease Progression in a Cohort of HIV-Positive Drug Users. Journal of Acquired Immune Deficiency Syndromes. 2009; 50(1):93-99.
  18. Duncan R, Shapshak P, Page JB, et al. Crack cocaine: effect modifier of RNA viral load and CD4 count in HIV infected African American women. Frontiers in Bioscience. 2007;12:488-495.
  19. Centers for Disease Control and Prevention Emergency department visits involving nonmedical use of selected prescription drugs – United States, 2004–2008.MMWR Morb Mortal Wkly Rep. 2010;59:705–709.
  20. Brick J. Handbook of the medical consequences of alcohol and drug abuse. New York, NY: The Haworth Press; 2004.