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Drug Dependence


The WHO defines drug dependence as:

“A state, psychic and sometimes  physical resulting  from taking a drug characterized by behavioral and other responses that always include a compulsion to take a drug on a continuous or periodic basis in order to experience its psychic effects, and some times to avoid discomfort of its absence”

Body systems become adopted in a way that the person has to take the drug, leading to tolerance and changes of toxicity e.g. morphine like drugs may cause respiratory depression.

Once the drug is stopped, since the body has adopted, it leads to withdrawal or abstinence symptoms, opposite to therapeutic effects. Morphine, an analgesic, producing sedation and calming effects if not provided, may cause pain, irritability and diarrhea. Thus leading to addiction.

CNS drugs are psychoactive drugs, acting by mesolimbic dopaminergic pathway on ventral tegmental areas, involved with behavior and emotion; show the phenomenon of drug dependence. When these drugs are prescribed, in a few percentage of people, produce euphoria, the feeling of well being. This euphoria compels them to take the drugs repeatedly due to which certain changes take place in the homeostasis by virtue of presence of drug.


  1. Euphoria
  2. Physical dependence- known now as dependence e.g. antihypertensive drugs have to be taken life long by the patients, bronchodilators and nitrates (glyceryl trinitrate) are other examples. These include non psychoactive drugs, individual is dependent but is not addiction
  3. Psychological dependence- known now as addiction, which is the compulsion to take the drug in spite of negative effects. More relapses and compulsion to take drugs occur e.g. cocaine addiction, but has no withdrawal symptoms, opoids have highly troublesome
  4. Abstinence/withdrawal syndrome

There are different symptoms and mechanisms of different drug abuse. The main problem is the denial by the patient.

Development of dependence

The first use of a drug is in one of four contexts

  1. Therapeutics,
  2. Recreational
  3. Instrumental,
  4. Cultural

The outcomes of use of drugs depend on:

The drug – its availability form and its ability to induce reinforcement

The individual: curious rebellious unhappy, vulnerable types, pleasure seeking, motivation, also the response to the drug

The culture: deprivation, constraints, peer groups, the age of instant gratification.

Commonly abused drugs

Common abused drugs/substances include

  1. Opiates and Narcotics
    Heroin (diacetylmorphine, highly lipophilic and short lived), opium, codeine (used in cough syrups), meperidine, hydromorphin
  2. Central Nervous System Stimulants
    Amphetamines (sympathomimetic), cocaine, dextroamphetamine, Methamphetamine, methylphenidate.
    Most commonly used stimulants are caffeine and nicotine, for which craving develops (psychological dependence)
  3. Central Nervous System Depressants
    (amobarbital, Pento barbital, Secobarbital)
    Benzodiazepines: (Valium, Ativan, Xanax)
    Chloral hydrate (was used as sedative hypnotic in young children), paraldehyde

Benzodiazepines are sedatives and anti anxiety drugs, used on continuous basis, which leads to dependence. Sleep cycle is disturbed and cause paradoxical problems in elderly

The most commonly used is alcohol, a social drink, which when taken within limits presents no problems.

  1. Hallucinogens
    LSD, Mescaline Psilocybin (Mushroom), Phencyclidine (Angel dust), Cannabis

Cannabis has medical importance and is anti cancer. They improve the quality of life but lead to distorted perception.

Causes, Incidence and Risk Factors

Drug abuse can lead to drug dependence or addiction. Drug dependence may also follow the use of drugs for physical pain relief.  The exact cause of drug abuse and dependence is not known. However, the genetic make-up of the individual (e.g. receptors for morphine), the pharmacology of the particular drug, peer pressure, emotional distress, anxiety, depression, and environmental stress are all factor which seem to be involved.


Drug abuse is simply excessive use of a drug or use of a drug for purposes for which it was not medically intended. There are some substances that do not cause addiction but do cause physical dependence e.g. (some blood pressure medications) and substances that cause addiction but not physical dependence (Cocaine).


Opiates and Narcotics
Symptoms of use
  • The first sign of addiction is denial
  • Needle marks on the skin in some cases (because of release of histamine on scratching
  • Scars from skin abscesses
  • Rapid heart rate
  • Constricted pupils (pin point) (dilated in cocaine)
  • Relaxed and/or euphoric state
  • Coma, respiratory depression leading to coma and death in high doses.
Symptoms of withdrawal
  • Anxiety and difficulty sleeping
  • Sweating
  • Runny nose (rhinorrhea)
  • Stomach cramps or diarrhea
  • Dilated pupils
  • Nausea and vomiting
  • Excessive sweating
  • Increase in blood pressure, pulse and temperature

Less potency drugs like methadone are given during withdrawal, otherwise patient may die.

Central Nervous System Stimulants
Symptoms of cocaine use
  • Euphoria (exaggerated feeling of well being)
  • Dilated pupils
  • Rapid heart rate
  • Restlessness and hyperactivity
Symptoms of cocaine withdrawal
  • Fatigue and malaise
  • Depression
  • Vivid and unpleasant dreams
Central Nervous System Depressants
Symptoms of alcohols use
  • Slurred speech
  • Lack of coordination
  • Decreased attention span
  • Impaired judgment
Symptoms of alcohol withdrawal
  • Anxiety
  • Tremors
  • Seizures
  • Increase in blood pressure, pulse, and temperature
  • Delirium
Symptoms of LSD use
  • Anxiety
  • Frightening hallucinations
  • Paranoid delusions
  • Blurred vision
  • Dilated pupils
  • Tremors

Drugs are categorized into A, B&C with class A being subject to stiffer control

Class A  Drugs (highly addictive)

Class B Drugs

Alfentanil Oral Preparations of Amphetamines
Cocaine Barbiturates
Heroin Codeine
Lofentamil Gluthethamide
LSD Pentazocine
Methadone Phenmetrazine
Morphine Pholcodine (cough syrup)
Ingectables of Class B  

  Class- C Drugs

Meprobamate (muscle relaxant)
Most benzodiazepines
Cannabis – became classified as a class C drug
Mazindol (used in anesthesia, added in January 2004


Drug intoxication and drug overdose may be accidental or intentional. Drug withdrawal symptoms can occur when use of substance is stopped or reduced. Withdrawal symptoms vary, depending on the abused substance. The onset of withdrawal symptoms depends on the length of time the drug normally stays within the body. Withdrawal can be life – threatening in some situations.

Treatment of drug dependency

  1. Detoxification
  2. Support
  3. Abstinence

Detoxification is the gradual withdrawal of an abused substance in a controlled environment. Sometimes a drug with a similar action is substituted during the withdrawal process to reduce the unpleasant symptoms and risks associated with withdrawals.

Drug abuse and dependence may lead to a fatal drug overdose. Replace from drug abstinence may occur and lead to recurrent dependence.

Complications of drug abuse

  1. Bacterial endocarditis
  2. Hepatitis
  3. Thrombophlebitis
  4. Pulmonary emboli
  5. Malnutrition
  6. Respiratory infections.
  7. Intravenous drug abuse
  8. Infection with HIV through shared needles.
  9. Drug induced loss of inhibitions may lead to unsafe sexual practices

Increase in various cancer rates e.g. lung and pharynx cancer, are associated with nicotine use, mouth and stomach cancer are associated with alcohol abuse and dependence

Drug Use

Drug is used for therapeutic purposes

Drug Abuse

When the same drug used for therapeutic purposes for treatment of particular condition, because of feeling of reward (e.g. pain relieving effect of analgesics) administered repeatedly is known as drug abuse.

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