Describe opioid poisoning and the drugs of abuse with the salient provisions of the NDPS Act.

Opioids

• Opium is the dried latex of the unripe capsule of Papaver somniferum, containing morphine (about 10%), codeine, thebaine, papaverine and noscapine. heroin (diacetylmorphine) is the semi-synthetic diacetyl derivative, more lipid-soluble and therefore faster acting; and the synthetics include pethidine, methadone, tramadol, buprenorphine and fentanyl, the last being of extreme potency
• Mechanism — agonism at mu, kappa and delta receptors, producing analgesia, euphoria, sedation and respiratory depression
• The classical triad of acute overdose — coma, pinpoint pupils, and respiratory depression. With non-cardiogenic pulmonary oedema, hypotension, hypothermia and reduced bowel sounds. Death is from respiratory failure
• Note that the pupils dilate terminally as hypoxia supervenes, and that they may not be pinpoint in pethidine or where another drug has been taken — so wide pupils do not exclude an opioid
• Naloxone is both the treatment and a diagnostic test: 0.4 to 2 mg intravenously, repeated and then by infusion. Its half-life is shorter than that of most opioids, so the patient may relapse into respiratory depression as it wears off and must be observed for hours — this is a recurring cause of death after apparently successful treatment. It is particularly short relative to methadone and buprenorphine
• Withdrawal — lacrimation, rhinorrhoea, yawning, piloerection ("cold turkey"), mydriasis, cramps, diarrhoea, myalgia and craving. It is intensely unpleasant but not usually life-threatening in an adult, in contrast to alcohol or barbiturate withdrawal — but neonatal withdrawal in the infant of a dependent mother can be fatal
• Chronic use — needle tracks and thrombosed veins; skin abscesses; infective endocarditis; HIV, hepatitis B and C; constipation; malnutrition; and amenorrhoea
• The loss OF tolerance phenomenon — tolerance falls rapidly during abstinence, so a dependent person who resumes their usual dose after release from prison, discharge from rehabilitation or a period in hospital is at high risk of fatal overdose. This is one of the commonest patterns in opioid deaths and is entirely predictable

Other Drugs of Abuse

The NDPS Act 1985

• The Narcotic Drugs and Psychotropic Substances Act 1985 governs narcotic drugs and psychotropic substances in India — their cultivation, manufacture, possession, sale, purchase, transport and consumption
• Punishment is graded by quantity, which is the central scheme of the Act: small quantity — up to 1 year or fine; intermediate (more than small, less than commercial) — up to 10 years; and commercial quantity — 10 to 20 years rigorous imprisonment and a heavy fine, with bail severely restricted and, for repeat offences involving specified quantities, the possibility of the death penalty (now discretionary rather than mandatory)
• Section 27 deals with consumption; and Section 64A provides immunity from prosecution for an addict who volunteers for treatment at a recognised centre — a provision of direct practical importance which doctors should know and tell patients about
• Section 39 permits the release of an addict on probation for treatment
• The medical role — examination of a suspected addict or trafficker; examination of a "body packer" who has swallowed sealed packets of drugs, in whom rupture of a packet causes massive fatal overdose and who is managed with whole bowel irrigation and, where a packet has ruptured or obstruction occurs, surgery; certification for treatment and rehabilitation; and evidence in court
• Preservation — blood, urine, hair (which records use over months), and the substance itself, sealed and with the chain of custody maintained

Recognising the Common Toxidromes

Applied Aspects

• Observe for several hours after naloxone, and use an infusion for methadone, buprenorphine and any long-acting opioid; the antidote outlasts nothing
• Warn about lost tolerance at every discharge from prison, hospital or rehabilitation; the usual dose becomes a fatal dose, and this is preventable by advice alone
• Do not give beta-blockers in cocaine toxicity; unopposed alpha stimulation worsens the hypertension and coronary spasm. Use benzodiazepines
• Tell addicts about section 64A; voluntary presentation for treatment confers immunity from prosecution, and fear of prosecution is the main barrier to seeking help
• Never attempt endoscopic removal in a body packer; rupture of a packet is rapidly fatal, and management is whole bowel irrigation with surgery if a packet leaks or obstructs
• Look for the complications of injecting — endocarditis, abscess, HIV and hepatitis — in every opioid presentation, since the overdose is often the least of the problems
• Consider inhalant abuse in street children; solvents are cheap and legal, sudden sniffing death is well described, and the chronic neurological damage is permanent
• The opioid triad is coma, pinpoint pupils and respiratory depression, but the pupils dilate terminally as hypoxia supervenes
• Pethidine may not produce miosis, so wide pupils do not exclude an opioid overdose
• Opioid withdrawal is unpleasant but rarely fatal in adults, unlike alcohol or barbiturate withdrawal, though it can kill a neonate
• Heroin is more lipid soluble than morphine, which is why it crosses into the brain faster and is more sought after
• Section 64A gives immunity to an addict who volunteers for treatment, and fear of prosecution is the main barrier to seeking help
• NDPS punishment is graded by quantity — small, intermediate and commercial — with bail severely restricted at the top
• Hair records drug use over months, and is taken alongside blood and urine where the history is disputed
• Naloxone is diagnostic as well as therapeutic, and a response establishes the toxidrome within minutes
• Bowel sounds separate anticholinergic from sympathomimetic — absent in the first and present in the second
• Clonus greater in the legs indicates serotonin syndrome, which is otherwise easily confused with a sympathomimetic state
• Fentanyl is of extreme potency, so a dose that looks trivial may be fatal and larger naloxone doses are needed
• Sudden sniffing death follows exertion or startle in solvent abusers, through myocardial sensitisation to catecholamines
• MDMA causes hyponatraemia from excess water drinking with inappropriate ADH, as well as hyperthermia
• Chewing tobacco and gutkha cause submucous fibrosis and oral carcinoma, and are a major Indian public health burden