Calcium-channel blocker overdose is a serious condition that can be life-threatening. The most dangerous types of calcium channel blockers in overdose are verapamil and diltiazem. These medications work by binding to the alpha-1 subunit of L-type calcium channels, which prevents the entry of calcium into cells. These channels are important for the functioning of cardiac myocytes, vascular smooth muscle cells, and islet beta-cells.

When managing a patient with calcium-channel blocker overdose, it is crucial to follow the standard ABC approach for resuscitation. If there is a risk of life-threatening toxicity, early intubation and ventilation should be considered. Invasive blood pressure monitoring is also necessary if hypotension and shock are developing.

The specific treatments for calcium-channel blocker overdose primarily focus on supporting the cardiovascular system. These treatments include:

1. Fluid resuscitation: Administer up to 20 mL/kg of crystalloid solution.

2. Calcium administration: This can temporarily increase blood pressure and heart rate. Options include 10% calcium gluconate (60 mL IV) or 10% calcium chloride (20 mL IV) via central venous access. Repeat boluses can be given up to three times, and a calcium infusion may be necessary to maintain serum calcium levels above 2.0 mEq/L.

3. Atropine: Consider administering 0.6 mg every 2 minutes, up to a total of 1.8 mg. However, atropine is often ineffective in these cases.

4. High dose insulin – euglycemic therapy (HIET): The use of HIET in managing cardiovascular toxicity has evolved. It used to be a last-resort measure, but early administration is now increasingly recommended. This involves giving a bolus of short-acting insulin (1 U/kg) and 50 mL of 50% glucose IV (unless there is marked hyperglycemia). Therapy should be continued with a short-acting insulin/dextrose infusion. Glucose levels should be monitored frequently, and potassium should be replaced if levels drop below 2.5 mmol/L.

5. Vasoactive infusions: Catecholamines such as dopamine, adrenaline, and/or noradrenaline can be titrated to achieve the desired inotropic and chronotropic effects.

6. Sodium bicarbonate: Consider using sodium bicarbonate in cases where a severe metabolic acidosis develops.

Paracetamol levels should be measured 4 hours after ingestion. If the patient arrives at the emergency department more than 4 hours after ingestion, the levels can be taken immediately. However, if the patient has not reached the 4-hour mark yet, the measurement should be postponed until they reach that time.

Further Reading:

Paracetamol poisoning occurs when the liver is unable to metabolize paracetamol properly, leading to the production of a toxic metabolite called N-acetyl-p-benzoquinone imine (NAPQI). Normally, NAPQI is conjugated by glutathione into a non-toxic form. However, during an overdose, the liver’s conjugation systems become overwhelmed, resulting in increased production of NAPQI and depletion of glutathione stores. This leads to the formation of covalent bonds between NAPQI and cell proteins, causing cell death in the liver and kidneys.

Symptoms of paracetamol poisoning may not appear for the first 24 hours or may include abdominal symptoms such as nausea and vomiting. After 24 hours, hepatic necrosis may develop, leading to elevated liver enzymes, right upper quadrant pain, and jaundice. Other complications can include encephalopathy, oliguria, hypoglycemia, renal failure, and lactic acidosis.

The management of paracetamol overdose depends on the timing and amount of ingestion. Activated charcoal may be given if the patient presents within 1 hour of ingesting a significant amount of paracetamol. N-acetylcysteine (NAC) is used to increase hepatic glutathione production and is given to patients who meet specific criteria. Blood tests are taken to assess paracetamol levels, liver function, and other parameters. Referral to a medical or liver unit may be necessary, and psychiatric follow-up should be considered for deliberate overdoses.

In cases of staggered ingestion, all patients should be treated with NAC without delay. Blood tests are also taken, and if certain criteria are met, NAC can be discontinued. Adverse reactions to NAC are common and may include anaphylactoid reactions, rash, hypotension, and nausea. Treatment for adverse reactions involves medications such as chlorpheniramine and salbutamol, and the infusion may be stopped if necessary.

The prognosis for paracetamol poisoning can be poor, especially in cases of severe liver injury. Fulminant liver failure may occur, and liver transplant may be necessary. Poor prognostic indicators include low arterial pH, prolonged prothrombin time, high plasma creatinine, and hepatic encephalopathy.

In adults, urinary alkalinisation is initiated when the salicylate level exceeds 500 mg/L (>3.6 mmol/L). For children, the threshold is set at a salicylate concentration of > 350 mg/L (2.5 mmol/L).

Further Reading:

Salicylate poisoning, particularly from aspirin overdose, is a common cause of poisoning in the UK. One important concept to understand is that salicylate overdose leads to a combination of respiratory alkalosis and metabolic acidosis. Initially, the overdose stimulates the respiratory center, leading to hyperventilation and respiratory alkalosis. However, as the effects of salicylate on lactic acid production, breakdown into acidic metabolites, and acute renal injury occur, it can result in high anion gap metabolic acidosis.

The clinical features of salicylate poisoning include hyperventilation, tinnitus, lethargy, sweating, pyrexia (fever), nausea/vomiting, hyperglycemia and hypoglycemia, seizures, and coma.

When investigating salicylate poisoning, it is important to measure salicylate levels in the blood. The sample should be taken at least 2 hours after ingestion for symptomatic patients or 4 hours for asymptomatic patients. The measurement should be repeated every 2-3 hours until the levels start to decrease. Other investigations include arterial blood gas analysis, electrolyte levels (U&Es), complete blood count (FBC), coagulation studies (raised INR/PTR), urinary pH, and blood glucose levels.

To manage salicylate poisoning, an ABC approach should be followed to ensure a patent airway and adequate ventilation. Activated charcoal can be administered if the patient presents within 1 hour of ingestion. Oral or intravenous fluids should be given to optimize intravascular volume. Hypokalemia and hypoglycemia should be corrected. Urinary alkalinization with intravenous sodium bicarbonate can enhance the elimination of aspirin in the urine. In severe cases, hemodialysis may be necessary.

Urinary alkalinization involves targeting a urinary pH of 7.5-8.5 and checking it hourly. It is important to monitor for hypokalemia as alkalinization can cause potassium to shift from plasma into cells. Potassium levels should be checked every 1-2 hours.

In cases where the salicylate concentration is high (above 500 mg/L in adults or 350 mg/L in children), sodium bicarbonate can be administered intravenously. Hemodialysis is the treatment of choice for severe poisoning and may be indicated in cases of high salicylate levels, resistant metabolic acidosis, acute kidney injury, pulmonary edema, seizures and coma.

Theophylline is a medication used to treat severe asthma. It is a bronchodilator that comes in modified-release forms, which can maintain therapeutic levels in the blood for 12 hours. Theophylline works by inhibiting phosphodiesterase and blocking the breakdown of cyclic AMP. It also competes with adenosine on A1 and A2 receptors.

Achieving the right dose of theophylline can be challenging because there is a narrow range between therapeutic and toxic levels. The half-life of theophylline can be influenced by various factors, further complicating dosage adjustments. It is recommended to aim for serum levels of 10-20 mg/l six to eight hours after the last dose.

Unlike many other medications, the specific brand of theophylline can significantly impact its effects. Therefore, it is important to prescribe theophylline by both its brand name and generic name.

Several factors can increase the half-life of theophylline, including heart failure, cirrhosis, viral infections, and certain drugs. Conversely, smoking, heavy drinking, and certain medications can decrease the half-life of theophylline.

There are several drugs that can either increase or decrease the plasma concentration of theophylline. Calcium channel blockers, cimetidine, fluconazole, macrolides, methotrexate, and quinolones can increase the concentration. On the other hand, carbamazepine, phenobarbitol, phenytoin, rifampicin, and St. John’s wort can decrease the concentration.

The clinical symptoms of theophylline toxicity are more closely associated with acute overdose rather than chronic overexposure. Common symptoms include headache, dizziness, nausea, vomiting, abdominal pain, rapid heartbeat, dysrhythmias, seizures, mild metabolic acidosis, low potassium, low magnesium, low phosphates, abnormal calcium levels, and high blood sugar.

Seizures are more prevalent in acute overdose cases, while chronic overdose typically presents with minimal gastrointestinal symptoms. Cardiac dysrhythmias are more common in chronic overdose situations compared to acute overdose.

SIADH is a medical condition that is not brought on by lithium toxicity. However, lithium toxicity does have its own distinct set of symptoms. These symptoms include nausea and vomiting, diarrhea, tremors, ataxia, confusion, increased muscle tone, clonus, nephrogenic diabetes insipidus, convulsions, coma, and renal failure. It is important to note that SIADH and lithium toxicity are separate conditions with their own unique characteristics.

First-generation antipsychotics, also known as conventional or typical antipsychotics, are powerful blockers of the dopamine D2 receptor. However, each drug in this category has different effects on other receptors, such as serotonin type 2 (5-HT2), alpha1, histaminic, and muscarinic receptors.

These first-generation antipsychotics are known to have a high incidence of extrapyramidal side effects, which include rigidity, bradykinesia, dystonias, tremor, akathisia, tardive dyskinesia, and neuroleptic malignant syndrome (NMS). NMS is a rare and life-threatening reaction to neuroleptic medications, characterized by fever, muscle stiffness, changes in mental state, and dysfunction of the autonomic nervous system. NMS typically occurs shortly after starting or increasing the dose of neuroleptic treatment.

On the other hand, second-generation antipsychotics, also referred to as novel or atypical antipsychotics, are dopamine D2 antagonists, except for aripiprazole. These medications are associated with lower rates of extrapyramidal side effects and NMS compared to the first-generation antipsychotics. However, they have higher rates of metabolic side effects and weight gain.

It is important to note that serotonin syndrome shares similar features with NMS but can be distinguished by the causative agent, most commonly the serotonin-specific reuptake inhibitors.

Urinary alkalinisation aims to achieve a urinary pH of 7.5-8.5. This process helps enhance the elimination of salicylates. It is important to regularly monitor urinary pH, ideally on an hourly basis.

Further Reading:

Salicylate poisoning, particularly from aspirin overdose, is a common cause of poisoning in the UK. One important concept to understand is that salicylate overdose leads to a combination of respiratory alkalosis and metabolic acidosis. Initially, the overdose stimulates the respiratory center, leading to hyperventilation and respiratory alkalosis. However, as the effects of salicylate on lactic acid production, breakdown into acidic metabolites, and acute renal injury occur, it can result in high anion gap metabolic acidosis.

The clinical features of salicylate poisoning include hyperventilation, tinnitus, lethargy, sweating, pyrexia (fever), nausea/vomiting, hyperglycemia and hypoglycemia, seizures, and coma.

When investigating salicylate poisoning, it is important to measure salicylate levels in the blood. The sample should be taken at least 2 hours after ingestion for symptomatic patients or 4 hours for asymptomatic patients. The measurement should be repeated every 2-3 hours until the levels start to decrease. Other investigations include arterial blood gas analysis, electrolyte levels (U&Es), complete blood count (FBC), coagulation studies (raised INR/PTR), urinary pH, and blood glucose levels.

To manage salicylate poisoning, an ABC approach should be followed to ensure a patent airway and adequate ventilation. Activated charcoal can be administered if the patient presents within 1 hour of ingestion. Oral or intravenous fluids should be given to optimize intravascular volume. Hypokalemia and hypoglycemia should be corrected. Urinary alkalinization with intravenous sodium bicarbonate can enhance the elimination of aspirin in the urine. In severe cases, hemodialysis may be necessary.

Urinary alkalinization involves targeting a urinary pH of 7.5-8.5 and checking it hourly. It is important to monitor for hypokalemia as alkalinization can cause potassium to shift from plasma into cells. Potassium levels should be checked every 1-2 hours.

In cases where the salicylate concentration is high (above 500 mg/L in adults or 350 mg/L in children), sodium bicarbonate can be administered intravenously. Hemodialysis is the treatment of choice for severe poisoning and may be indicated in cases of high salicylate levels, resistant metabolic acidosis, acute kidney injury, pulmonary edema, seizures and coma.

There are various specific remedies available for different types of poisons and overdoses. The following list provides an outline of some of these antidotes:

Poison: Benzodiazepines
Antidote: Flumazenil

Poison: Beta-blockers
Antidotes: Atropine, Glucagon, Insulin

Poison: Carbon monoxide
Antidote: Oxygen

Poison: Cyanide
Antidotes: Hydroxocobalamin, Sodium nitrite, Sodium thiosulphate

Poison: Ethylene glycol
Antidotes: Ethanol, Fomepizole

Poison: Heparin
Antidote: Protamine sulphate

Poison: Iron salts
Antidote: Desferrioxamine

Poison: Isoniazid
Antidote: Pyridoxine

Poison: Methanol
Antidotes: Ethanol, Fomepizole

Poison: Opioids
Antidote: Naloxone

Poison: Organophosphates
Antidotes: Atropine, Pralidoxime

Poison: Paracetamol
Antidotes: Acetylcysteine, Methionine

Poison: Sulphonylureas
Antidotes: Glucose, Octreotide

Poison: Thallium
Antidote: Prussian blue

Poison: Warfarin
Antidote: Vitamin K, Fresh frozen plasma (FFP)

By utilizing these specific antidotes, medical professionals can effectively counteract the harmful effects of various poisons and overdoses.

Enzyme-inducing anticonvulsants have been found to enhance the metabolism of ethinyl estradiol and progestogens. This increased breakdown diminishes the effectiveness of the oral contraceptive pill (OCP) in preventing pregnancy. Some examples of enzyme-inducing anticonvulsants include carbamazepine, phenytoin, phenobarbitol, and topiramate.

On the other hand, non-enzyme-inducing anticonvulsants are unlikely to have an impact on contraception. Some examples of these anticonvulsants are sodium valproate, clonazepam, gabapentin, levetiracetam, and piracetam.

It is important to note that lamotrigine, although classified as a non-enzyme-inducing anticonvulsant, requires special consideration. While there is no evidence suggesting that the OCP directly affects epilepsy, there is evidence indicating that it reduces the levels of lamotrigine in the bloodstream. This reduction in lamotrigine levels could potentially compromise seizure control and increase the likelihood of experiencing seizures.

During the first trimester of pregnancy, the use of warfarin can lead to a condition known as fetal warfarin syndrome. This condition is characterized by nasal hypoplasia, bone stippling, bilateral optic atrophy, and intellectual disability in the baby. However, if warfarin is taken during the second or third trimester, it can cause optic atrophy, cataracts, microcephaly, microphthalmia, intellectual disability, and both fetal and maternal hemorrhage.

There are several other drugs that can have adverse effects during pregnancy. For example, ACE inhibitors like ramipril can cause hypoperfusion, renal failure, and the oligohydramnios sequence if taken during the second and third trimesters. Aminoglycosides such as gentamicin can lead to ototoxicity and deafness in the baby. High doses of aspirin can result in first trimester abortions, delayed onset labor, premature closure of the fetal ductus arteriosus, and fetal kernicterus. However, low doses of aspirin (e.g. 75 mg) do not pose significant risks.

Benzodiazepines like diazepam, when taken late in pregnancy, can cause respiratory depression and a neonatal withdrawal syndrome. Calcium-channel blockers, if taken during the first trimester, can cause phalangeal abnormalities, while their use in the second and third trimesters can lead to fetal growth retardation. Carbamazepine can result in hemorrhagic disease of the newborn and neural tube defects. Chloramphenicol can cause gray baby syndrome. Corticosteroids, if taken during the first trimester, may cause orofacial clefts.

Danazol, if taken during the first trimester, can cause masculinization of the female fetuses genitals. Finasteride should not be handled by pregnant women as crushed or broken tablets can be absorbed through the skin and affect male sex organ development. Haloperidol, if taken during the first trimester, may cause limb malformations, while its use in the third trimester increases the risk of extrapyramidal symptoms in the newborn.

Heparin can lead to maternal bleeding and thrombocytopenia. Isoniazid can cause maternal liver damage and neuropathy and seizures in the baby. Isotretinoin carries a high risk of teratogenicity, including multiple congenital malformations and spontaneous abortion.