Week 22 Pharmacology

Drugs of abuse

  • Dependence
    • When a person can only function normally in the presence of the drug and manifests as a physical disturbance when the drug is removed(withdrawal)
  • Addiction
    • A compulsive use of a substance despite negative consequences.
    • The physical or psychological dependence on an agent that often mediates a reward sensation when consumed.
  •  Tolerance
    • An organism decreases its response to a drug so a higher dose is required to elicit the same effect.


Specific drugs of abuse:

  • Opioids
    • Resp depression, miosis, constipation, drowsiness, nausea, vomiting, addiction, tolerance
  •  Cocaine
    • CNS stimulant, monoamine reptake inhibitor, inhibit dopamine transporter, Na channel blocker, can cause vasoconstriction, tachycardia, local anaesthetic, itching, hallucination
    • OD – hyperthermia, HTN, arrhythmias, death
  • Other stimulants- amphetamine, nicotine, caffeine – increase monoamines in CNS
  • Psychedelic agents- LSD, ecstasy, PCP
    • Delusions, hallucinations, mydriasis, increase temp, dry mouth, HTN, tachycardia, sweating, numbness, weakness, tremor, nausea
    • Acts on dopamine and adrenergic receptors
    • Not very addictive
  •  Benzodiazepines
    • GABA A agonist
  •  Alcohol
    • GABA A agonist, NMDA antagonist
  •  Marijuana/Canabis
    • Sedative
    • Act via canabinoid receptor
    • Dry mouth, decreased intra ocular pressure, tachycardia, muscle relaxation, sensation of heat or cold.
  • Inhalants


Withdrawal Syndromes

  • Opioid
    • Early – agitation, anxiety, muscle aches, increased tearing, insomnia, Sweating, yawning, runny nose
    • Late – abdo cramp, diarrhoea, dilated pupils, piloerection, nausea, vomiting
  • Cocaine
    • Low mood, cravings, fatigue, insomnia, vivid dreams, increased appetite, physical slowing
  • Alcohol
    • Tremor, seizures, agitation, insomnia, nausea, vomiting, transient hallucinations, diaphoresis
    • Begins 6-24hrs after ceasing, can last for upto 1 week
  • Nicotine
    • Low mood, anxiety, cough, increased appetite, intense craving, depersonalisation, drowsy, headache, irritability, concentration difficulty.
    • Starts 2-3hrs after last cigarette
  • Benzodiazepines
    • Seizure, strokes,hallucinations if you stop tranquilizers suddenly
  • Marijuana
    • sleep difficulties including insomnia and strange dreams
    • mood swings/irritability
    • depression
    • anxiety/nervousness
    • restlessness/physical tension
    • reduced appetite
    • nausea
    • cravings to smoke cannabis


Carbon monoxide poisoning

  • Light headedness, confusion, vertigo, headache
  • Binds stronger to Hb than O2
  • Rx – 100% oxygen

Hydrocarbons (not that important)

Hydrocarbon poisoning such as that of benzene and petroleum usually occurs accidentally by inhalation or ingestion of these cytotoxic chemical compounds. Intravenous or subcutaneous injection of petroleum compounds with intent of suicide or abuse is an extraordinary event that can result in local damage or systemic toxicity such as tissue necrosis, abscess formation, respiratory system failure and partial damage to the kidneys, the brain and the nervous system

RX : Stabilization of the airway is always the first priority of treatment in patients with hydrocarbon poisoning. Give supplemental oxygen to all patients. Early intubation, mechanical ventilation, and use of positive end-expiratory pressure may be warranted in a patient with inadequate oxygenation, severe respiratory distress, or a decreased level of consciousness.

Organophosphate poisoning

  • Inhibit Acetylcholinesterase –> Too much cholinergic stimulus –> diarrhoea, increased salivation, increased sweating, lacrimation, urination, vomiting, miosis, HTN, hypoglycaemia, anxiety, convulsion, generalised weakness, resp depression, bradycardia


Heavy Metal Poisoning

  • Lead Toxicity, Mercury Toxicity, Arsenic Toxicity and Iron Toxicity
  • RX : Decontamination, resuscitation with airway and hemodynamic support.
  • Discuss with Local Poisons regarding elimination treatment as it differ for each heavy metal


Viva questions:

  • What is dependence, tolerance etc.
  • Tell me about the effects of acute intoxication with _______ .
  • What is withdrawal / give an example
  • Tell me about alcohol/ benzo/ opioid withdrawal.
  • Tell me about Heroin
  • Tell me about cocaine
  • Tell me about amphetamines
  • Tell me about carbon monoxide poisoning.