Emergency Drugs- Clinical Assessment

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Atropine injection

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Atropine is indicated for the temporary blockade of severe or life-threatening muscarinic effects.

The intramuscular use of atropine in the form of a pen injector is indicated for the treatment of poisoning by susceptible organophosphorus nerve agents having cholinesterase activity as well as organophosphorus or carbamate insecticides.

MOA: Atropine binds to and inhibits muscarinic acetylcholine receptors, competitively blocking the effects of acetylcholine and other choline esters.

Dosage:

Adverse effect: High doses of atropine may cause palpitation, dilated pupils, difficulty swallowing, hot dry skin, thirst, dizziness, restlessness, tremor, fatigue and ataxia.

Toxic doses of atropine lead to restlessness and excitement, hallucinations, delirium and coma.

In cases of severe intoxication, atropine can cause a circulatory collapse, leading to a decline in blood pressure and respiratory failure that may ensue in death following paralysis and coma.

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DEXTROSE

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Glucose pharmaceutical formulations (oral tablets, injections) are indicated for caloric supply and carbohydrate supplementation in case of nutrient deprivation.

It is also used for metabolic disorders such as hypoglycemia.

Adverse effects: The administration of glucose infusions can cause fluid and solute overloading resulting in dilution of the serum electrolyte concentrations, overhydration, congested states, or pulmonary edema. Hypersensitivity reactions may also occur.

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Dopamine injection

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Indication: It is used in the treatment of cardiogenic shock due to myocardial infarction, trauma, endotoxic septicemia, open-heart surgery, renal failure, and chronic cardiac decompensation as in congestive failure

MOA: Dopamine is a precursor to norepinephrine in noradrenergic nerves and is also a neurotransmitter in certain areas of the central nervous system. Dopamine produces positive chronotropic and inotropic effects on the myocardium, resulting in increased heart rate and cardiac contractility. Also acts as an antagonist to the five Dopamine subtypes (D1,D2,D3,D4,D5)

Adverse effect: Spasm or closing of eyelids, nausea, vomiting, cardiac arrhythmias, involuntary movements of the body including the face, tongue, arms, hand, head, and upper body; hypotension, haemolytic anaemia, urinary retention, duodenal ulcer, ataxia, abdominal pain, dry mouth, nightmares, tachypnoea, bruxism, confusion, and insomnia.

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Oxygen

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Oxygen is an essential element for human survival used in clinical conditions in which there is a lack of oxygen, such as, but not limited to, anoxia, hypoxia or dyspnea.Indication: Oxygen therapy in clinical settings is used across diverse specialties, including various types of anoxia, hypoxia or dyspnea and any other disease states and conditions that reduce the efficiency of gas exchange and oxygen consumption such as respiratory illnesses, trauma, poisonings and drug overdoses.

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EPINEPHRINE/ADRENALINE INJECTION

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This medication is used in emergencies to treat very serious allergic reactions to insect stings/bites, foods, drugs, or other substances.

Epinephrine works quickly to improve breathing, stimulate the heart, raise a dropping blood pressure, reverse hives, and reduce swelling of the face, lips, and throat.

Indication: Cardiac arrest, severe anaphylactic reaction, severe angioedema.

Mechanism of Action: Epinephrine acts on both alpha and beta-adrenergic receptors. The mechanism of the rise in blood pressure is 3-fold: a direct myocardial stimulation that increases the strength of ventricular contraction (positive inotropic action), an increased heart rate (positive chronotropic action), and peripheral vasoconstriction.

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NITROGLYCERIN INJECTION:

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Nitroglycerin injection is used to treat hypertension (high blood pressure) during surgery or to control congestive heart failure in patients who have had a heart attack. It may also be used to produce hypotension (low blood pressure) during surgery.

Mechanism of Action: Nitroglycerin is a vasodilator, a medicine that opens blood vessels to improve blood flow. It is used to treat angina symptoms, such as chest pain or pressure, that happens when there is not enough blood flowing to the heart.

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What is the best option for decontaminating the gut in poisoning?

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The best method of preventing absorption of ingested poisons is with the use of activated charcoal. Administration of activated charcoal is the easiest, safest, and most effective method of decontamination of the gut in almost all situations.

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Antidotes for Opiates (e.g. codeine, heroin, pethidine, morphine, methadone)

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These drugs cause depression of conscious state and hypoventilation. Particular attention should be paid to the maintenance of the airway and adequate ventilation. The specific antidote naloxone is highly effective.

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Antidote for paracetamol poisoning.

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Overdose of this drug is common and can be fatal. Initial symptoms are mild with nausea, vomiting, and sometimes abdominal pain. Hepatic failure and death may follow in days to weeks.

Acetylcysteine is the specific antidote and if given within 8 hours may largely prevent hepatic damage.

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Antidote for Anticholinesterases (e.g. insecticides)

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These substances cause severe cholinergic effects including vomiting, diarrhoea, bradycardia, hypotension, hypersalivation, bronchospasm, urinary incontinence, muscle weakness, constricted pupils, and pulmonary edema.

Poisoning may occur with skin exposure or inhalation, as well as with oral ingestion.

The specific antidote is atropine.

Pralidoxime, which is an acetylcholinesterase reactivator, may also be useful, particularly if administered in conjunction with atropine.

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Antidote for aliphatic hydrocarbons (e.g. kerosene, petroleum)

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Hydrocarbons cause irritation of the gastrointestinal tract, with common symptoms being abdominal pain, vomiting, and diarrhoea.

Their most dangerous toxic effects occur when they are aspirated into the lungs causing a chemical pneumonitis. Hydrocarbons are not absorbed by activated charcoal so this should not be given.

Patients who have any signs or symptoms of aspiration pneumonitis (e.g. fever, cough, dyspnea, wheeze) should be given oxygen, admitted for observation, and administration of intravenous antibiotics should be considered.

Patients with severe vomiting and diarrhoea may need intravenous hydration.

There is no specific antidote for these chemicals.

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Antidote for Alkali ingestion (e.g. bleach, drain cleaner)

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There is no specific antidote; the treatment is supportive only. Ingestion of an alkaline substance causes damage to the oropharynx and oesophagus. Household bleach (5% sodium hypochlorite) is not a very strongly alkaline substance and is unlikely to cause serious injury.

These patients need only symptomatic treatment with intravenous fluids and admission for observation. Stronger alkalis such as drain cleaner may cause severe chemical burns the complications of which include airway obstruction and oesophageal or gastric perforation. These patients should be admitted for rehydration and consideration of upper gastrointestinal endoscopy to determine the extent of the damage.

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Antidotes for Oral anticoagulants (e.g. warfarin, rat poison)

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Overdose of these substances causes prolongation of the prothrombin time and increased risk of bleeding.

Vitamin K reverses the effect of oral anticoagulants over 12 to 24 hours whereas fresh frozen plasma provides immediate replacement of coagulation factors.

The potency of rat poisons vary ­ some may require large doses of vitamin K over several weeks.

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Antidotes for Beta-adrenergic antagonists (e.g. propranolol, atenolol)

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Beta-blocker overdose causes bradycardia, AV node block and hypotension, sometimes complicated by bronchospasm, congestive cardiac failure, and confusion.

Use adrenaline infusion.

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antidote for iron overdose

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Overdose of iron initially causes vomiting, diarrhoea, abdominal pain, and sometimes haematemesis. After a variable quiescent period during which these gastrointestinal symptoms resolve, the patient may develop shock and hypoglycaemia plus cardiac, hepatic, and renal failure.

The specific antidote is desferrioxamine but supportive care including intravenous fluid and glucose (if necessary) is important as well.

Iron is not well absorbed by activated charcoal.

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Antidotes for Benzodiazepines (e.g. diazepam)

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These substances are very safe in overdose generally causing only drowsiness. Supportive care and observation is usually all that is necessary.

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Antidote for overdose of phenytoin

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In overdose, phenytoin causes cerebellar dysfunction (nystagmus, ataxia, dysarthria, nausea, and vomiting) plus confusion, coma and paradoxically, seizures. Treatment is essentially supportive. Diazepam should be used to control seizure.

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Antidote for Carbon monoxide (e.g. car exhaust)

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This odourless and colourless gas competes with oxygen for the binding sites on the haemoglobin molecule. Toxic effects include headache, nausea, confusion, coma, seizures, and cardiac arrhythmias. Treatment for symptomatic patients is with 100% oxygen for at least 12 hours.

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What to give in tachycardia?

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Propanolol

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Antidote to chloroquine poisoning

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This drug is highly toxic in overdose causing hypotension and cardiac arrhythmias. Treatment involves adrenaline and very large doses of diazepam.

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Local Anaesthetics

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Local anaesthetic agents are used to provide anaesthesia through local wound infiltration, nerve blocks or regional techniques.

1) Lignocaine is the agent of choice for local wound infiltration.

2) Lignocaine with adrenaline. The addition of adrenaline helps control bleeding and also extends the duration of anaesthesia.

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Sedatives and Induction Agents

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These drugs are used to depress the conscious state either for sedation or general anaesthesia.

1) Ketamine has anaesthetic and analgesic properties and is less likely to produce hypotension than other sedative agents. It also has a mild bronchodilator action which makes it useful when anaesthetising patients with asthma.

2) Thiopentone is a barbiturate with a short action because of rapid distribution. Its main adverse effects relate to cardiorespiratory depression.

3) Midazolam is a short-acting benzodiazepine. It has powerful amnestic properties and produces less cardiorespiratory depression than thiopentone. It is a fairly safe and useful anaesthetic induction agent in the critically ill and is also used to sedate children and agitated patients.

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Anticholinergics

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Anticholinergic drugs block the effects of acetylcholine at muscarinic receptors.

The most commonly used anticholinergic agent is atropine. This drug is used for the treatment of bradycardia due to increased vagal tone, to block the cholinergic effects of drugs such as suxamethonium in children, and to reverse some of the adverse effects of anticholinesterase (organophosphate) poisoning.

Ipratropium is used in the treatment of asthma and benztropine is used in the treatment of oculogyric crisis.

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Opioid analgesics

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Opioid agents are mainly used for their analgesic and sedative actions.

Morphine is usually used in the treatment of acute myocardial infarction and pulmonary oedema.

Pethidine is mainly used as an analgesic. This is a highly addictive drug even after a few doses.

Fentanyl is a short acting narcotic used to sedate patients prior to painful procedures or intubation (often in combination with midazolam).

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Antiemetics

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Anti-emetic drugs are used for the temporary relief of nausea and vomiting.

Metoclopramide (brand name: Maxolon) should not be given to children less than 16 years of age due to the high incidence of acute dystonic reactions. It should also not be given to patients with bowel obstruction.

Prochlorperazine (brand name: Stemetil) is also useful for the treatment of vertigo as well as nausea and vomiting. It should not be given to children less than 16 years of age.

Promethazine (brand name: Phenergan) is a weaker antiemetic than prochlorperazine and is more sedating. It can be given intravenously, intramuscularly or orally.

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Corticosteroids

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Although very useful in the treatment of asthma, anaphylaxis and many other conditions, the beneficial effects of these drugs are delayed for several hours at least. Hydrocortisone has marked mineralocorticoid effects.

Dexamethasone has virtually no mineralocorticoid effects. Prednisolone has moderate mineralocorticoid effects.

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Antiepileptics

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The first line drug in the treatment of epilepsy is diazepam. Phenytoin is useful for the treatment of idiopathic epilepsy but is less effective for seizures due to other causes.

Barbiturates such as phenobarbitone are powerful anti-epileptics but also cause cardiorespiratory depression and marked depression of conscious state often necessitating intubation and ventilation.

Diazepam is a safe and effective agent for the termination of seizures. It may be given intravenously or rectally.

Phenytoin must be given by slow intravenous injection. Rapid infusion of concentrated solutions may cause hypotension.

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Antiarrhythmics

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1) Lignocaine Lignocaine shortens the action potential duration. It is the drug of first choice in the treatment of ventricular tachycardia.

2) Propranolol Propranolol is occasionally used to delay conduction through the atrioventricular (AV) node in the treatment of supraventricular tachycardia or atrial fibrillation.

3) Amiodarone Amiodarone prolongs the action potential duration. It is used in the treatment of both ventricular and atrial arrhythmias.

4) Verapamil Verapamil is a calcium channel antagonist and depresses sinus node automaticity and AV node conduction. It is therefore used to treat supraventricular tachyarrhythmia.

5) Digoxin Digoxin is used to control the ventricular rate in atrial fibrillation.

6) Adenosine Adenosine is a very short acting agent used in the treatment of supraventricular tachycardia.

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What is used to treat ventricular tachycardia due to digoxin toxicity.

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phenytoin

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What is used in the treatment of ventricular tachycardia due to theophylline overdose.

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Propranolol

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Antihypertensives

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Several different drugs are available for the management of hypertensive emergencies.

1) Hydrallazine is a direct acting arteriodilator. It should not be used in patients with ischaemic heart disease who are not being treated with a beta-blocker.

2) Nifedipine is a direct-acting arterial vasodilator.

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Inotropic Agents

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Inotropic agents are used in the treatment of cardiogenic and distributive shock. All should be infused via a large vein. Adrenaline is an alpha- and beta-adrenergic agonist. It causes an increase in cardiac output and heart rate plus vasoconstriction.

Dopamine has similar effects to adrenaline but produces more tachycardia at higher doses.

Dobutamine has positive chronotropic and inotropic effects which are balanced by a mild degree of vasodilation so that myocardial oxygen demand is generally not increased.

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Diuretics

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Furosemide is a potent loop diuretic used in the treatment of fluid overload. Its main side effects are hypokalaemia and fluid depletion.

Frusemide is ineffective in the acute treatment of hypertension and should not be used except as an adjunct to other more powerful drugs.

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Muscle Relaxants

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Suxamethonium and Vecuronium

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Neuroleptics

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Haloperidol is the safest neuroleptic to use for sedation. It may be given intramuscularly or intravenously. Chlorpromazine is more likely to cause hypotension than haloperidol.

Diazepam can be used as a sedative for short defined periods of treatment to avoid addiction.

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Anti-asthma Drugs

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1) Salbutamol is a beta-2 adrenergic agonist. It is best given in the inhaled form (either via an inhaler or a nebulizer).

2) Ipratropium is used in the treatment of asthma and chronic obstructive pulmonary disease (COPD). It has a synergistic effect with salbutamol.

3) Corticosteroids

4) Aminophylline is a xanthine derivative that has been used for many years in the treatment of asthma. However, it is a weak bronchodilator and has no additional benefit over optimal doses of salbutamol. It also has a very narrow therapeutic margin and therefore has little place in the management of acute asthma.

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Intravenous Fluids

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1) Normal (0.9%) saline contains 154 mmol per liter of sodium chloride. It is the fluid of first choice in the treatment of hypovolaemia.

2) Dextrose 5% contains 50 g per liter of dextrose. It is distributed to the total body water space and is thus not suitable for emergency rehydration. Although it can be used as the sole maintenance fluid in the short term, prolonged administration of 5% dextrose alone may cause hyponatraemia, especially in children.

3) Dextrose 3% with 0.3 saline contains 51 mmol per liter of sodium chloride and 30 g per liter of dextrose. Its primary use is as a maintenance fluid (with potassium) in children. It may be suitable for rehydration of patients with mild or moderate dehydration.

4) Hartmann’s solution contains a mixture of ions similar to that of the extracellular fluid.

5) Plasma volume expanding solution (e.g. Haemaccel, Gelofusin): Colloids can be used for patients with hypovolaemic shock in association with crystalloid solutions.

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Drugs Used in Cardiac Arrest

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1) Adrenaline is a powerful endogenous catecholamine. The pharmacologic doses used in cardiac arrests far exceed the amounts usually produced by the adrenal glands. Adrenaline has both alpha- and beta-adrenergic agonist effects. It stimulates myocardial contraction, increases the heart rate, and raises the blood pressure.

2) Lignocaine is recommended for the treatment of ventricular fibrillation and ventricular tachycardia. Its effectiveness has not been proven but it is unlikely to be harmful.

3) Atropine is used in the treatment of asystole and severe bradycardia. It acts to block the effects of the vagus nerve on the heart.

4) Sodium bicarbonate is used to treat the metabolic acidosis associated with cardiac arrest. Its effectiveness has not been proven and it has many potential adverse effects.