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The term “dependency” was previously used to describe a severe form of substance abuse and drug addiction characterized by the triad of: (1) a psychological dependence or craving and the behavior involved in procurement of the drug; (2) physiologic dependence, with withdrawal symptoms on discontinuance of the drug; and (3) tolerance, ie, the need to increase the dose to obtain the desired effects. The terms “dependency” and “abuse” were dropped in DSM-5 in favor of the single term “substance use disorder,” ranging from mild to severe. Many patients could have a severe and life-threatening abuse problem without ever being dependent on a drug. Substance use disorder is a treatable, chronic medical illness. Clinicians and health care systems must work against bias toward people with substance use disorder. Medication-assisted treatment is available for a number of substance use disorders and is a key element in their management.

There is accumulating evidence that an impairment syndrome exists in many former (and current) drug users. It is believed that drug use produces damaged neurotransmitter receptor sites and that the consequent imbalance produces symptoms that may mimic other psychiatric illnesses. “Kindling”—repeated stimulation of the brain—renders the individual more susceptible to focal brain activity with minimal stimulation. Stimulants and depressants can produce kindling, leading to relatively spontaneous effects no longer dependent on the original stimulus. These effects may be manifested as mood swings, panic, psychosis, and occasionally overt seizure activity. The imbalance also results in frequent job changes, partner problems, and generally erratic behavior. Patients with PTSD frequently have treated themselves with a variety of drugs. Chronic abusers of a wide variety of drugs exhibit cerebral atrophy on CT scans, a finding that may relate to the above symptoms. Early recognition is important, mainly to establish realistic treatment programs that are chiefly symptom-directed.

The clinician faces three problems with substance use disorders: (1) the prescribing of substances such as sedatives, stimulants, or opioids that might produce dependency; (2) the treatment of individuals who have already misused drugs, most commonly alcohol; and (3) the detection of illicit drug use in patients presenting with psychiatric symptoms. The usefulness of urinalysis for detection of drugs varies markedly with different drugs and under different circumstances (pharmacokinetics is a major factor) (see also Chapter 5). Water-soluble drugs (eg, alcohol, stimulants, opioids) are eliminated in a day or so. Lipophilic substances (eg, barbiturates, tetrahydrocannabinol) appear in the urine over longer periods of time: several days in most cases, 1–2 months in chronic marijuana users. Sedative drug determinations are quite variable, amount of drug and duration of use being important determinants. False-positives can be a problem related to ingestion of some legitimate medications (eg, phenytoin for barbiturates, phenylpropanolamine for amphetamines, chlorpromazine for opioids) and some foods (eg, poppy seeds for opioids, coca leaf tea for cocaine). Manipulations can alter the legitimacy of the testing. Dilution, either in vivo or in vitro, can be detected by checking urine-specific gravity. Addition of ammonia, vinegar, ...

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