A 30 year-old female under psychiatric treatment was admitted to the poison control centre with restlessness, upward deviation of the eyes, torticollis, abnormal movement of the tongue and tachyarrythmia. Blood pressure was 80/50 mmHg, pupils were dilated, ECG revealed supraventricular tachyarrythmia.
1. What is your provisional diagnosis?
-Phenothiazine toxicity.
2. Discuss the mechanism of action of this drug.
(A) Receptor blockade:
- Dopamine Receptor blockade: extrapyramidal and neuroendocrine effects
- Alpha adrenergic receptor blockade : postural hypotension and reflex tachycardia
- Muscarinic receptor blockade: sinus tachycardia, blurred vision, dry mouth, decreased intestinal motility and urine retention
- Histamine (H1) receptor blockade: sedation
(B) Cardiovascular effects:
-Hypotension due to vasodilatation of blood vessels and direct myocardial depression
-Conduction abnormalities and arrhythmias
(C) Central nervous system effects:
-Depression of :
(1) Cerebral cortex ➡ coma
(2) Respiratory center ➡ respiratory failure
(3) Dopamine receptors ➡ extrapyramidal manifestations
(4) Chemoreceptor trigger zone ➡ anti-emesis
(5) Heat regulating center ➡ hypothermia or hyperthermia & increased prolactin ➡ amenorrhoea galactorrhoea
3. Mention other CNS manifestations of the consumed drugs.
-Ataxia, stupor and coma. Hypothermia is common and occasionally hyperthermia may occur TRUE OR FALSE (a) Gastric lavage is absolutely contraindicated in hydrocarbon poisoning :False, gastric lavage can be carried out after insertion of cuffed endotracheal tube to prevent aspiration peumonia. (b) Smokeless powder used in firearm weapons is more potent than black powder :True, as 1 volume of smokeless powder will lead to the generation of 900ml of gas on ignition compared to 300ml when using black powder. DEFINE(a) Tardieu’s spots : These are small pin-point collections of blood seen under the skin, sclera or conjunctiva and under serous membranes such as the pleura, pericardium and peritoneum.(b) Concussion : It is a clinical state of transient loss of consciousness due to temporary impaired cerebral functions. MCQs(1) All are causes of post-traumatic acutre renal failure except :(a) DIC(b) Crush syndrome(c) Venous air embolism(d) Excessive use of vasopressor agents (2) Coagulative necrosis occurs in case of poisoning by :(a) Ammonium hydroxide(b) Phenol(c) Alkaline potash(d) Sodium hydroxidehea syndrome (c) Mention other CNS manifestations of the consumed drugs- Ataxia, stupor and coma. Hypothermia is common and occasionally hyperthermia may occur TRUE OR FALSE (a) Gastric lavage is absolutely contraindicated in hydrocarbon poisoning :False, gastric lavage can be carried out after insertion of cuffed endotracheal tube to prevent aspiration peumonia. (b) Smokeless powder used in firearm weapons is more potent than black powder :True, as 1 volume of smokeless powder will lead to the generation of 900ml of gas on ignition compared to 300ml when using black powder. DEFINE(a) Tardieu’s spots : These are small pin-point collections of blood seen under the skin, sclera or conjunctiva and under serous membranes such as the pleura, pericardium and peritoneum.(b) Concussion : It is a clinical state of transient loss of consciousness due to temporary impaired cerebral functions. MCQs(1) All are causes of post-traumatic acutre renal failure except :(a) DIC(b) Crush syndrome(c) Venous air embolism(d) Excessive use of vasopressor agents (2) Coagulative necrosis occurs in case of poisoning by :(a) Ammonium hydroxide(b) Phenol(c) Alkaline potash(d) Sodium hydroxide
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