Overdoses

Question 1

How do amphetamines work?

Answer 1

Amphetamine exerts its behavioral effects by altering the use of epinephrine and norepinephrineas neuronal signals in the brain, primarily incatecholamine neurons in the reward and executive function pathways of the brain

Question 2

What type of drugs are amphetamines?

Answer 2

Amphetamines are CNS and cardiovascular stimulants

Question 3

What do amphetamine overdoses lead to?

Answer 3

Agitation, tachy­cardia, hypertension, widely dilated pupils, trismus and sweating

Question 4

What detrimental processes can happen in severe amphetamine overdose?

Answer 4

In more severe cases, hyperthermia, disseminated intravascular coagulation, rhabdomyolysis, acute kidney injury and hyponatraemia predominate

Question 5

How long are amphetamines detectable?

Answer 5

Amphetamines are detectable in the urine for 2-3 days

Question 6

How would you manage an amphetamine overdose?

Answer 6

Agitation is controlled by diazepam 10–20 mg i.v. or chlorpro­mazine 50–100 mg i.m.

The peripheral sympathomimetic actions of amfetamines are antagonized by β- adrenoceptor blocking drugs.

If hyperthermia is present, dantrolene 1 mg/ kg body weight i.v. is used.

Question 7

How do benzodiazepines work?

Answer 7

Benzodiazepines enhance GABA, decreasing the excitability of neurons

Question 8

What does a benzodiazepine overdose lead to?

Answer 8

Benzodiazepines produce drowsiness, ataxia, dysarthria and nystagmus. Coma and respiratory depression develop in severe intoxication.

Question 9

How would you manage benzodiazepine intoxication?

Answer 9

If respiratory depression is present in patients who have severe benzodiazepine poisoning, flumazenil 0.5–1.0 mg i.v. is given in an adult and this dose often needs repeating.

Flumazenil use often avoids ventilation.

It is contraindicated in mixed tricyclic antidepressant (TCA)/benzodiazepine poisoning and in those with a history of epilepsy because it may cause convulsions.

Question 10

How do cannabis overdoses present?

Answer 10

Intravenous injection leads to watery diarrhoea, tachycardia, hypotension and arthralgia.

Heavy users suffer impairment of memory and attention and poor academic performance. There is an increased risk of anxiety and depression

Question 11

How would you manage cannabis intoxication?

Answer 11

Reassurance is usually the only treatment required, although sedation with intravenous diazepam 10–20 mg i.v. in an adult or chlorpromazine 50–100 mg i.m. in an adult is sometimes required.

Hypotension requires i.v. fluids.

Question 12

How does cocaine work?

Answer 12

Block­ade of noradrenaline (norepinephrine), reuptake produces tachycardia, and inhibition of serotonin reuptake induces hal­lucinations

Cocaine also enhances CNS arousal by potenti­ating the effects of excitatory amino acids

Cocaine is also a powerful local anaesthetic and vasoconstrictor

Question 13

How does a cocaine intoxication present?

Answer 13

After initial euphoria, cocaine produces agitation, tachycar­dia, hypertension, sweating, hallucinations, convulsions, metabolic acidosis, hyperthermia, rhabdomyolysis and ventricular arrhythmias

Dissection of the aorta, myocarditis, myocardial infarction, dilated cardiomyopathy, subarachnoid haemorrhage, and cerebral haemorrhage and infarction also occur

Question 14

If a young person present with stroke or an MI, what do you have to check?

Answer 14

If they use cocaine

Question 15

How would you manage a cocaine overdose?

Answer 15

Diazepam 10–20 mg i.v. is used to control agitation and con­vulsions

Active external cooling should be used for hyper­thermia

Question 16

How does GHB intoxication present?

Answer 16

Poisoning with GHB is characterised by aggressive behav­iour, ataxia, amnesia, vomiting, drowsiness, bradycardia, respiratory depression and apnoea, seizures and characteristically coma, which is short­-lived

Question 17

How would you manage a GHB intoxication?

Answer 17

In a patient who is breathing spontaneously, the manage­ment of GHB poisoning is primarily supportive with oxygen supplementation and the administration of atropine for per­sistent bradycardia, as necessary

Those who are severely poisoned will require mechanical ventilation, although recovery is usually complete within 6–8 hours

Question 18

How does a lithium overdose present?

Answer 18

Features of intoxication include thirst, polyuria, diarrhoea and vomiting and in more serious cases impairment of consciousness, hypertonia and convulsions; irreversible neu­rological damage occurs

Acute massive over­dose may produce concentrations of 5 mmol/L (34.7 mg/L) without causing toxic features, whereas chronic toxicity is associated with neurological features at concentrations >1.5 mmol/L (6.94 mg/L).

Question 19

How would you manage a lithium overdose?

Answer 19

Forced diuresis with sodium chloride 0.9% is effective in increasing elimination of lithium, though haemodialysis is far superior and should be undertaken particularly if neurological features are present

Question 20

How does an opioid overdose present?

Answer 20

Cardinal signs of opiate poisoning are pinpoint pupils, reduced respiratory rate and coma

Hypothermia, hypoglycaemia and convulsions are occasionally observed in severe cases.

In severe heroin overdose, non­-cardiogenic pulmo­nary oedema has been reported.

Question 21

How would you manage an opioid overdose?

Answer 21

Naloxone 1.2–2.0 mg i.v. will reverse at least partially severe respiratory depression and coma

The duration of action of naloxone is often less than the drug taken in over­ dose, e.g. methadone, which has a very long half­-life; infusion of naloxone is often required

Question 22

In what people is a paracetamol overdose partially dangerous?

Answer 22

People with pre­-existing liver disease, those suffering from acute or chronic starvation (patients not eating for a few days for example due to a recent febrile illness or dental pain), those suffering from anorexia nervosa and other eating disorders, those receiving enzyme ­inducing drugs, and those with HIV infection should be considered to be at greater risk and given treatment at plasma paracetamol concentrations lower than those nor­mally used for interpretation

Question 23

How does a paracetamol overdose present?

Answer 23

Following the ingestion of an overdose of paracetamol, patients usually remain asymptomatic for the first 24 hours or at the most develop anorexia, nausea and vomiting

Liver damage is not usually detectable by routine liver function tests until at least 18 hours after ingestion of the drug

Liver damage usually reaches a peak, as assessed by measure­ment of alanine transferase (ALT) activity and prothrombin time (INR), at 72–96 hours after ingestion

Question 24

How would you manage a paracetamol overdose?

Answer 24

The treatment protocol is dependent on the time of presenta­tion

Acetylcysteine (antioxidant) has emerged as an effective protective agent provided that it is administered within 8–10 hours of ingestion of the overdose (Can administer later, but efficacy goes down)

Question 25

What is the risk of Acetylcysteine treatment?

Answer 25

Up to 15% of patients treated with intravenous acetyl­ cysteine (20.25­h regimen) develop rash, angio­-oedema, hypotension and bronchospasm

These reactions, which are related to the initial bolus, are seldom serious and discontinuing the infusion is usually all that is required

Question 26

How do salicylate overdoses present?

Answer 26

Salicylates stimulate the respiratory centre, increase the depth and rate of respiration, and induce a respiratory alka­losis

Compensatory mechanisms, including renal excretion of bicarbonate and potassium, result in a metabolic acidosis

Thus, tachypnoea, sweating, vomiting, epigastric pain, tin­nitus and deafness develop

Question 27

How would you manage a salicylate overdose?

Answer 27

Fluid and electrolyte replacement is required and special attention should be paid to potassium supplementation. Severe metabolic acidosis requires at least partial correction with the administration of sodium bicarbonate intravenously.

Patients whose plasma salicylate concentrations are in excess of 500 mg/L (3.62 mmol/L) should receive urine alkalinisation

Haemodialysis is the treatment of choice for severely poisoned patients (plasma salicylate concentration >700 mg/L; >5.07 mmol/L)