Drug overdose Flashcards
What is drug overdose?
The ingestion or application of a drug or other substances in quantities greater than are recommended or generally practiced.
Drug overdose can occur accidently or deliberately. TRUE OR FALSE?
TRUE
List the drugs that are mostly used intentionally for self poisoning?
- Benzodiazepines
- analgesics
- antidepressants
What are the drugs that are mostly at risk and provide examples for each?
- Drugs with a narrow therapeutic window e.g digoxin and theophylline
- Drugs with steep dose response curves e.g warfarin, sulhonylurea der
- Drugs that are enzyme inhibitors e.g Ketoconazole, erythromycin
- drugs that are enzymes inducers e.g rifampicin, carbamazepine
- Drugs with high toxic potential e.g aminoglycosides
Give examples of patients that are most at risk?
- Polymorbidity
- Polypharmacy
- Chronic disease
- Non compliance
- Self treatment
- Abuse
What equation can be used to calculate the therapeutic window/index?
Therapeutic window = Dose causing toxicity/Dose providing efficacy
Provide some examples of drugs that have a very narrow therapeutic window/index?
- Aminoglycoside antibiotics
- Anticoagulants
- Aspirin
- Digoxin
- Lithium
- Tricyclic antidepressants
What are the 6 steps required for the treatment of drug overdose?
- Immediate measures evaluation
- Supportive measures
- Prevent absorption
- Elimination
- Antidotes
- Pschiatric assessment
What ocurs in Evaluation for drug poisoning treatment?
- Recognition of poisoning (pill bottles/examination)
- Identification of agents involved
- Assessment of severity
- -prediction of toxicity
What does the ABC stand for in supportive care after drug poisoning?
A- airway
B- Breathing
C- Circulation
What ocurs in supportive measures for drug poisoning treatment?
- ABC
- Protect airway
- Vital signs, mental status, pupil size
- Pulse oximetry, cardiac monitoring, ECG
- Cervical immobilization if suspect trauma
- Rule out hypoglycaemia
What occurs in gastric lavage?
- Flexible tube is inserted through the nose into the stomach
- Stomach contents are then suctioned via tube
- A solution of saline is injected into the tube
- Not be used in unconscious patients unless intubated
What steps are taken in the preventing absorption phase after drug poisoning?
- Gastric lavage
- Induced vomiting - not recommended routinely due to risk of aspiration
- Activated charcoal
What does activated charcoal do?
- Absorbs toxic substances or irritants, inhibiting GI absorption
- Given as a single oral dose of 25-100g
- Repititve doses useful to enhance the elimination of certain drugs e.g theophylline
What substances does charcoal not absorb?
- Petroleum distillates
- Inorganic acid and alkali
- Alcohol
- Metal ions
- Cyanide
What types of medication are given in renal
elimination?
-Medications thta stimulate urination or defecation to increase the release/elimination of the drug out of the body
What is infused in forced alkaline diuresis?
-Infusion of large amounts of NS+NAHCO3
What types of drug does forced alkaline diuresis help to eliminate?
-acidic drugs that are mainly excreted by the kidney e.g salicylates
What issues can be caused by forced alkaline diuresis?
Can cause serious electrolyte disturbance
What types of dialysis are reserved for severe poisoning?
Hemodialysis and haemoperfusion
Hemodialysis and haemoperfusion can be used temporarily or as long term if kidneys are damaged due to overdose. TRUE OR FALSE?
TRUE
What are antidotes?
They are agents witha specific action against the activity or effect of drugs involved in poisoning cases
List and give examples of each antidote mechanisms
- Pharmacological antagonists
e. g naloxone (opiate poisoning) and ethanol (methanol poisoning) - Enhance physiological function to compensate
e. g Physostigmine (belladona alkaoid poisoning) - Restore active site of drug target
e. g Pralidoxime (pesticide poisoning) - Bypass block
e. g Glucagon (beta blocker poisoning) - Sequester poison
e. g Digibind (digoxin poisoning) - speed up excretion
e. g chloride is used as an antidote for bromide and iodide overdose
Paracetamol overdose causes toxic reactions with protein and nucleic acids, which leads to hepatoxicity. TRUE OR FALSE?
TRUE
Explain the 4 stages clinical features of paracetamol drug overdose?
Stage 1:
(0-5 to 24hrs) - No symptoms, vomiting and nausea
Stage 2:
(24hrs to 72hrs) - Subclinical elevations of hepatic aminotransferases, elevation of prothrombin, liver enlargement and tenderness, renal function abnormalities
Stage 3:
(72-96 hrs) - confusion (hepatic encephalopathy), lactic acidosis, hyperammonemia, hypoglycemia
Stage 4:
(4 days to 2 weeks) - Recovery phase that usually begins by day 4
How is paracetamol overdose managed, explain what ecah component does?
- Activated charcoal - may reduce absorption by 50 to 90%
- Acetylcysteine (antidote) a glutathione precursor (limits the formation and accumulation of NAPQI
- Methionine p.o - protects liver from damage
- Specialist advice for liver transplantation
What are the indications for liver transplantation?
- Acidosis (pH greater than 7.3)
- Prothrombin time less than 100 sec
- Creatinine greater than 300mcg
- Grade 3 encephalopathy
What are the functions of Aspirin?
- Analgesic
- Antipyretic
- Anti-inflammatory
- Anti platelet
Aspirin is not a type of NSAID. TRUE OR FALSE?
FALSE
What concentration in plasma does aspirin have to be considered as intoxication?
40 to 50 mg/dl
Why does metabolic acidosis occur during aspirin overdose?
Because ketogenisis is inhibited
An acidic pH promotes the movement of salicylate into the tissues. TRUE OR FALSE?
TRUE
Why does respiratory alkalosis occur?
Due to hyperventilation (CO2 exhalation increases)
Why does electrolyte imbalance occur during aspirin overdose?
- Increased renal excretion of bicarbonates, NA+, K+ follow
- Increased pulmonary insensible losses
- Vomiting
Actiavted charcoal is known to reduce the amount of activated salycilate by 50-80%. TRUE OR FALSE?
TRUE
Fluid replacement is not important in the management of salicylate toxicity. TRUE OR FALSE?
FALSE
What are the major ways in which fluid is lost in aspirin overdose?
- Tachypnea
- Vomiting
- Hypermetabolic state
- Insensible perspiration
What is the most important management for aspirin overdose?
Through urine alkalinization with sodium bicarbonates
What does urine alkalinization with sodium bicarbonates result in?
Enhanced excretion of ionized acid form of salicylate
How can alkalinization be achieved?
By giving a bolus 1-2 mEq/kg followed by IV infusion of 3 ampules of sodium bicarbonate in 1 L of D5W
What are the indications for hemodialysis?
- Renal failure
- Congestive heart failure
- Acute lung injury
- Persistant CNS disturbance
- Progressive deteriorative vital signs
- Salicylate concentration acute
Opioids bind to what specific receptors?
Specific opioid receptors in the CNS
What are the characteristics of opiates overdose?
- Respiratory depression (breathing slows, sometimes to a stop)
- Pinpoint pupils
- Decreased level of consciousness
- Hypotension and bradycardia (HR slows, blue lips, nails due to insufficient O2 in blood)
What is an important feature in opioid poisoning?
Pinpoint pupils
What two types of drugs are most common in drug overdose?
Heroin and morphine
What is the antidote for opiate overdose?
Naloxone
How does Naloxone act as an antidote?
It is a competitive antagonist at opioid receptors
What is the elimination half life of naloxone?
60 TO 90 minutes
Repeated administration/infusion of naloxone may be necessary. TRUE OR FALSE?
TRUE
Pesticides are not organophosphate. TRUE OR FALSE?
FALSE
What are organophosphate?
They are irreversible anticholinesterases
What are the nicotinic signs in pesticide poisoning?
- Twitching
- Fasciculations
- Muscle weakness
- Elevated Bp
What are the muscarinic signs in pesticide poisoning?
- Bronchoconstriction
- Increase secretion
- Sweating
- GI
- Miosis
What are the CNS signs in pesticide poisoning?
- Anxiety
- Restlessness
- Confusion
- Headache
What is the antidote for pesticide poisoning?
Pralidoxime, i.v for several days
What is the AchE regenerator called?
Oxime
What does oxime do?
It hydrolyzes the phosphorylated AChE
Pralidoxime is positively charged so does not enter the CNS. TRUE OR FALSE?
TRUE
The effects of organophosphate poisoning on the CNS is irreversible. TRUE OR FALSE?
TRUE
Silmutaneous use of atropine is required to control muscarinic excess. TRUE OR FALSE?
TRUE
Why is pretreatment with reversible inhibitors required?
To protect against excessive AchE inhibition when possibly lethal poisoning is anticipated
