Drug overdose

Drug overdose
Specialty	Emergency medicine

The term drug overdose (or simply overdose or OD) describes the ingestion or application of a drug or other substance in quantities greater than are recommended or generally practiced. An overdose is widely considered harmful and dangerous as it can result in death.

Classification

The word "overdose" implies that there is a safe dosage; therefore, the term is commonly only applied to drugs, not poison. Drug overdoses are sometimes caused intentionally to commit suicide or as self-harm, but many drug overdoses are accidental and are usually the result of either irresponsible behavior or the misreading of product labels. Drug overdose often happens as a result of the use of multiple drugs with counter indications simultaneously (for instance, heroin/certain prescription pain medications and cocaine/amphetamines/alcohol.) Usage of illicit drugs that are of unexpected purity, in large quantities, or after a period of abstinence can also induce overdose. Cocaine users that inject intravenous can overdose accidentally as the margin between an optimal flash and an overdose is small.

A common unintentional overdose in young children involves multi-vitamins containing iron. Iron is a component of the hemoglobin molecule in blood, used to transport oxygen to living cells. When taken in small amounts, iron allows the body to replenish hemoglobin, but in large amounts it causes severe pH imbalances in the body. If this overdose is not treated with chelation therapy, it can lead to death or permanent coma.

Signs and symptoms

Symptoms of overdose occur in various forms:

• Exaggerated form of normal action (e.g., sleepiness on antiepileptics, hypoglycemia on insulin)
• Other effects due to chemical properties of the medication (e.g., metabolic acidosis in aspirin, liver failure due to paracetamol)
• Non-specific symptoms due to central nervous system irritation (e.g., confusion, vertigo, nausea, vomiting, delirium, seizures)

Causes

Common types of drugs that are overdosed on:

• Barbiturates
  • Amobarbital
  • Seconal
  • Nembutal
• Benzodiazepines
  • Diazepam
  • Alprazolam
  • Temazepam
  • Triazolam
• Opioids
  • Morphine
  • Heroin
  • Methadone
  • Oxycodone
• Stimulants
  • Methamphetamine
  • Cocaine
• Ethyl Alcohol
  • Alcoholic beverages

• Drug "cocktails", or a combination of numerous drugs

Diagnosis

Diagnosis of an overdosed patient is generally straightforward if the drug is known. However, it can be very difficult if the patient cannot (or refuses to) state what drug they have overdosed on. At times, certain symptoms and signs exhibited by the patient, or blood tests, can reveal the drug in question. Even without knowing the drug, most patients can be treated with general supportive measures.

In some instances, antidotes may be administered if there is sufficient indication that the patient has overdosed on a particular type of medication.

Treatment

Initial measures

Once in hospital, establishing a stable airway, breathing rate and circulatory system is an essential first step. Ventilation is considered when there is a low respiratory rate or when blood gases show the person to be hypoxic. The next necessary step is to treat for shock. Investigations should be carried out in labs to help identify the drug(s) at hand such as glucose, urea and electrolytes, paracetamol levels and salicylate levels. Monitoring of the patient should continue before and throughout the treatment process, with particular attention to temperature, pulse, respiratory rate, blood pressure, urine output, electrocardiography (ECG) and O₂ saturation.

Specific treatment

Specific measures vary between the causative agents used. Blood plasma toxicology will depend upon the suspected agent such as measuring paracetamol levels in unconscious patients, or those suspected otherwise to have overdosed on the drug. Specific antidotes for common agents include:

• Benzodiazepines – Flumazenil.
• β-Blockers - Atropine, but glucagon and dextrose if atropine fails. If unresponsive, consider aortic balloon pumps.
• Carbon monoxide - 100% oxygen and monitoring.
• Anticoagulants - If major bleed is present, treat with vitamin K and provide prothrombin complex concentrate.
• Opiates - Naloxone, but high-dose opiate abusers may require methadone to combat withdrawal.

Prevention

• Refrain from mixing depressant drugs like alcohol, barbiturates, benzodiazepines, and opiates together.
• Start with small amounts, in order to estimate the potency of a drug.
• Be careful when taking a drug after a period of abstinence, as your tolerance may be drastically lowered.
• If you have a pharmaceutical chemical, make sure it is not expired. Toxicity can increase drastically.

Misconceptions

Deaths caused by adulterated drugs, most commonly heroin, are often incorrectly attributed to overdose. In this case the "overdose" is actually caused by toxicity from a buildup of various adulterant chemicals in the body over time, or a complication from the buildup of an otherwise inert adulterant.

Negative drug-drug interactions have sometimes been misdiagnosed as an acute drug overdose, occasionally leading to the assumption of suicide.

Additionally, recent psychological research indicates that "overdose" may be, in many cases, a misnomer. Most deaths attributed to heroin overdose, for example, are not technically due to "overdose" in the pharmacological sense: in most cases, Canadian researcher Shepard Siegel found, heroin abusers died taking the same dose of heroin they normally injected. The principles of classical conditioning may provide a framework for understanding how heroin abusers can die taking the same dose of heroin they have taken many times before. There is compelling evidence that taking heroin in a new or different environment than usual may lead to overdose. In the terms of Pavlovian conditioning, the environment where the addict usually takes the drug (for example, if he always injects in the same room with the same people) serves as the conditioned stimulus, while the drug effect of heroin serves as the unconditioned stimulus. The body tends to try to maintain homeostasis, so it creates a compensatory response to counteract the effects of the drug. In the case of heroin, which decreases pain sensitivity and slows breathing, the body's compensatory response would be to increase pain sensitivity and speed up breathing. As the environment (CS) and drug effect (US) are paired over and over, the environment alone becomes sufficient to evoke the body's compensatory response to heroin. This compensatory response, triggered by the environmental cues alone, is the conditioned response. As Pavlov's dogs learned to salivate at the ring of a bell because the bell was often paired with food, a heroin user's body creates a chemical, opposing response to heroin when the proper environmental cues are present. For this reason, the heroin abuser becomes able to take larger and larger doses of the drug, because his body creates a stronger and stronger compensatory response to its effects. "Overdose" often (more than half the time) occurs when the heroin abuser injects in a new environment. In this case, the environmental cues are not present, so the body does not produce the compensatory response required to make the usual large dose of heroin tolerable. The result is often death.

Combined Drug Intoxication or Multiple Drug Intake, is mistakenly reported by news media as Drug overdose, but it is not the same. CDI does not require drug overdose to kill a person. Death is caused by the simultaneous use of too many drugs.

One of the most common drugs to be implicated in Combined Drug Intoxication deaths, or in non-lethal overdoses causing harm to the body is acetaminophen (or paracetamol as it is known in some countries), an analgesic that is available over the counter. While considered harmless and beneficial when taken at recommended dosages, acetaminophen can be acutely toxic to the liver when taken in amounts exceeding its recommended dosage; this toxicity is compounded when the drug is taken in combination with alcoholic beverages, especially by chronic drinkers and people with preexisting liver disease such as hepatitis. In addition, long-term use of acetaminophen at high dosage (and especially concurrent with alcohol) is a common cause of chronic damage to the liver. See the main article on Paracetamol for more information.

Since Paracetamol is not considered, by itself, an addictive medication, complications arising from its overuse are often referred to in medical literature as Paracetamol Poisoning. However, since paracetamol is often contained in formulations which contain other drugs with a high potential for abuse, it is often ingested in amounts far exceeding its therapeutic dose in order to get a "high" from the coexisting drug. Examples include over-the-counter cough syrup and cold remedies which include, along with paracetamol, dextromethorphan, a cough suppressant that, when taken in high amounts, can cause hallucinations and euphoria. Because of its availability as an over-the-counter preparation in most jurisdictions (in brands such as Robitussin), dextromethorphan abuse is particularly popular among teenagers because it is easy to obtain. In addition to paracetamol, other medications like Guaifenesin, and pseudoephedrine are often present in dextromethorphan formulations, although many preparations contain dextromethorphan by itself, without any other drugs. It is common for a user to ingest an entire bottle of dextromethorphan-containing syrup to obtain the amount needed to get the wanted effects, which can deliver a dose of paracetamol (when present in the formulation) that is well above levels that can cause acute toxicity. Refer to the main article on non-medical use of dextromethorphan for more information.

Paracetamol is also combined with many narcotic analgesics that are, in most countries, strictly regulated as controlled substances because of their highly abusive potential. When patients or recreational users of these medications (examples include the brand names Vicodin, Darvocet, and Percocet) ingest these drug combinations in large amounts, they risk acute paracetamol poisoning (and sometimes overdose of the desired narcotic) or, over time, chronic hepatic damage. The abuse of these medications is on the increase, despite the fact that most physicians who prescribe them supply the patient with only a limited quantity in order to prevent their potential for chronic use and abuse. However, it is relatively simple for a user to find supplies of these medications, either on the street or by "jumping" from one physician to the other; dentists are often approached for prescriptions, since narcotic medications are given quite frequently to patients with dental pain, due to their efficacy in pain management for many dental problems. However, most dentists give prescriptions for a very limited supply of a narcotic analgesic, because, with treatment, most cases of tooth pain are relatively short-lived. NSDEA

Statistics

While they do not give separate figures for drug overdoses and other kinds of accidental poisoning, the National Center for Health Statistics report that 19,250 out of 30,000 people died of accidental poisoning in the U.S. in the year 2004.

See also

• List of drug-related deaths
• Combined Drug Intoxication
• Suicide
• Vitamin poisoning

External links

• Fact sheets on illicit drugs, overdose prevention, detox and harm reduction strategies.