Læknaneminn - 01.10.1996, Page 93

Overdoses and poisonings: physiological responses
Because a safe and effective antidote (Narcan,
naloxone) exists for opiate poisoning, it is routinely
given to patients who present with altered mental stat-
us. It is important to note that some opiates (e.g.
Lomotil) require large amounts of naloxone to achieve
reversal.
E. Withdrawal Toxidrome
This condition, which is similar to the sympathetic
toxidrome, is characterised by:
• Diarrhoea
• Mydriasis (dilated pupils)
• Piloerection
• Tachycardia (rapid heart beat)
• Lacrimation
• Yawning
• Cramps
• Seizures
• Hallucinations
Numerous drugs which have been administrated
chronically can cause a withdrawal toxidrome if they
are abruptly terminated. Among these are the foll-
owing.
• Alcohol
• Barbiturates
• Narcotics
• Chloral hydrate
• Benzodiazepines
• Other sedative-hypnotics
IV. SPECIFIC SYMPTOMS
A. Seizures
A number of drugs reveal themselves in the clinical
context by causing seizures. This may occur by various
mechanisms which include:
• Adrenergic sdmulation
• GABAnergic inhibition
• Cholinergic inhibition
• Abrupt withdrawal from certain drugs
• Associated trauma or infection
• Induction of hypoglycemia
• Cerebral hypoperfusion
• Systemic or tissue hypoxia
A useful mnemonic for remembering the drugs
which cause seizures is PLASTIC (copyright 1991,
James R. Roberts, M.D.).
P- Phenothiazines, PCP, Pesticide, Pentazocine,
Propoxyphene
L- Lead, Lithium, Lindane, Local anaesthetics, LSD
A- Anticholinergics, Antihistamines
S- Sympathomimetics, Strychnine, Salicylates
T- Tricyclic antidepressants, Theophylline
I- Insulin (oral hypoglycemics), Inderal, Isoniazid
C- Cocaine, Cafergot, Carbon Monoxide, Cyanide,
Camphor, Caffeine
Drug withdrawal may also result in seizures, especi-
ally withdrawal from ethanol, benzodiazepines, and
barbiturates.
B. Cardiac Signs
There is a constellation of fmdings associated with
overdose or poisoning by drugs which produce a fast
sodium channel blockade. This type of poisoning is
suggested by the presence of a wide QRS complex on
cardiac monitoring or electrocardiogram.
Other associated fmdings include:
• Ventricular arrhythmias (especially torsades de
pointes)
• Hypotension
• Varying degrees of atrioventricular block
• Heart failure
• Bradyarrhythmias
• Asystole
• Failure to capture with attempts at pacing
Many drugs can produce these effects, in therapeut-
ic doses and/or in overdose, among them:
• E-Blockers
• Antihistamines
• Orphenadrine
• Propoxyphene
• Cocaine
• Lidocaine
• Local Anaesthetics
• Cyclic Antidepressants
• Antiarrhythmics (Type IA): Procainamide, Quini-
dine, Disopyramide
• Antiarrhythmics (Type IC): Encainide, Flecainide
• Phenothiazines: Thioridazine, Mesoridazine
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