Opiates and opioids
Opiates are drugs derived directly from opium (e.g. morphine, codeine, and heroin); while opioids are a broad class of opiate analogues that have morphine-like activity (e.g. methadone).
About 350,000 Australians have used heroin, methadone and/or other opioids at sometime in their lives and about 57,000 Australians had used these drugs sometime in the year prior to the 2007 National Drug Household Survey .
The most commonly used illicit methadone is physeptone tablets followed by methadone syrup .
Around 268,000 Australians have used heroin at some time while only about 10% of these were recent users. Most recent users surveyed injected crystalline (‘rock’) or heroin powder, around 50% of whom injected from 1 to 3 times per day .
It was estimated that there were around 74,000 dependent heroin users in Australia in the year 2000 .
Opiate dependence is indicated if 3 or more of the following ICD-10 criteria are met:
- A strong desire or sense of compulsion to use
- Difficulties in controlling opiate-taking behaviour
- A physiological withdrawal state when opiate use has ceased or has been reduced, as evidenced by: 1) opiate withdrawal syndrome; or 2) use of opiates with the intention of relieving or avoiding withdrawal symptoms
- Evidence of tolerance, such that increased doses of opiates are required in order to achieve effects originally produced by lower doses
- Progressive neglect of alternative pleasures or interests because of opiate use, increased amount of time necessary to obtain or take opiates or to recover from its effects
- Persisting with opiate use despite clear evidence of overtly harmful consequences, such as depressive mood states consequent to periods of heavy substance use.
For more information see the definition of dependence syndrome on the World Health Organisation website.
Benzodiazepine use and health service utilisation
Dependence on benzodiazepines among heroin users is common. In a study of 222 users in Sydney, 91% had used benzodiazepines at some time, and 35% had injected them. Twenty-two percent of current benzodiazepine users were dependent .
Utilisation of health services by heroin users is high. In one study around 60% of current heroin users reported at least one visit to a general practitioner in the month prior to interview, and about half had been prescribed medications – most commonly benzodiazepines .
Depression is common among heroin–dependent individuals which substantially increases risk of suicide . Although treatment of opiate dependence is associated with improvements in depressive symptoms , some users will require targeted treatment for depression which could include antidepressants and psychological therapy . It is important, therefore, to undertake a thorough mental health assessment so appropriate interventions can be implemented.
Pharmacology of heroin
Heroin (diacetylmorphine) is a semi-synthetic derivative of morphine and a powerful opioid analgesic. During heroin synthesis, two acetyl esters are added to the morphine molecule which allows heroin to cross the blood-brain barrier more readily than its precursor morphine, accounting for the rapid onset of heroin’s effects. As heroin has lower affinity for opioid receptors than morphine, heroin is considered a pro-drug that exerts effects primarily via its first metabolite 6-monoacetylmorphine and to a lesser extent its second metabolite, morphine .
The highest concentration of 6-monoacetylmorphine can be reached within seconds to 2 minutes after heroin injection and can be detected in plasma for 1-3 hours. Peak heroin concentration following intranasal heroin use or inhalation (‘chasing the dragon’) can be reached within 2-5 minutes.
When injected, inhaled or snorted, heroin is metabolised primarily by the kidneys and excreted via urine in which it can be detected for up to 1.5 days . Oral, anal and intramuscular administration is not favoured as first-pass liver metabolism inhibits the intense ‘rush’ that is so desired by most users.
Effects, risks and harms of heroin use
Heroin is synthesised to morphine (see pharmacology), which then binds to opiate receptors in the brain and brain-stem. Acute effects include:
- intense euphoria
- clouded cognitive functioning
- bradycardia and bradypnea
- pinpoint pupils
- nausea and vomiting
- overdose can be fatal as respirations are depressed .
Longer term risks may include:
- tolerance and dependence
- blood born virus transmission and other risks associated with injecting
- depression and suicide
- pulmonary complications secondary to poor physical health
- respiratory depression
- severe constipation
- menstrual irregularity and infertility in women
- loss of libido .
Repeated exposure to opioids can lead to neurobiological adaptation, specifically a reduction in numbers of endogenous opioid receptors. The onset and the time course of withdrawal depend upon the half-life of the opioid used.
Heroin withdrawal manifests within 6-24 hours after last use, symptoms peak at 24-48 hours and reside within 5-10 days. Symptoms include:
- increased sweating
- urinary frequency
- abdominal cramps
- muscle spasm
- back aches
- pupillary dilatation
- elevated blood pressure
- disturbed sleep
- increased cravings for opioids .
Although heroin withdrawal is extremely unpleasant, it is not life threatening to users with no medical complications.
Methadone withdrawal has a similar presentation to heroin withdrawal, symptoms emerge within 36-48 hours after the last dose, and some low-grade symptoms can linger for 3-6 weeks .
Buprenorphine withdrawal is generally milder than withdrawal from heroin or methadone, symptoms typically emerge within three to five days of the last dose, and mild withdrawal features can continue for up to several weeks .
Planned withdrawal is not effective as a stand alone treatment as many users fail to complete withdrawal and relapse rates are high.
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