Opioids: Heroin, Fentanyl Analogues and Prescription Diversions

Seized heroin rarely consists of diacetylmorphine alone. Cutting agents serve two purposes: bulk extension (adulterants that increase the weight of the product without pharmacological cost) and potentiation (adulterants that mimic or enhance the opioid effect at the dose point). Common adulterants in seized heroin across multiple jurisdictions:

• Caffeine: the most commonly detected adulterant globally, present in 60-80 per cent of seized brown heroin samples in European monitoring data (EMCDDA Drug Market Insights 2023). Its combination with heroin lowers the melting point of the mixture, facilitating volatilisation for smoking.
• Paracetamol (acetaminophen): common in South Asian and UK seizures. The paracetamol-heroin combination is associated with the brown-sugar formulation and impairs GC-MS quantification if not resolved from the diacetylmorphine peak.
• Quinine: historically common in US East Coast heroin seizures in the 1970s-1990s. Now largely replaced by caffeine or fentanyl.
• Fentanyl as a cutting adulterant: the most dangerous development in the US heroin supply since approximately 2014. Fentanyl is approximately 50-100 times more potent than morphine at equivalent doses; contamination of heroin batches with even trace fentanyl (microgram quantities) has driven overdose fatalities. The DEA's 2023 drug threat assessment notes that virtually all seized "heroin" in the US is now fentanyl or fentanyl-mixed product, with genuine heroin (diacetylmorphine) constituting less than 5 per cent of seizures by sample count.
• Levamisole: a veterinary antihelminthic increasingly found as a cocaine adulterant but also appearing in UK and EU heroin seizures.
• Diphenhydramine: an antihistamine with sedative properties, added to potentiate the subjective effect of lower-purity heroin. Found in US West Coast seizures.

The morphine-codeine-papaverine (MCP) alkaloid signature is an opium-source attribution tool. Opium from different geographic origins carries characteristic ratios of the four major alkaloids: morphine, codeine, papaverine, and noscapine (also called narcotine). These ratios reflect the Papaver somniferum chemotype grown in the source region, which is influenced by climate, soil, and cultivar selection. The Southwest Asian chemotype (Afghanistan, Pakistan) produces higher-codeine, lower-papaverine opium; the Southeast Asian chemotype (Myanmar) produces a different ratio profile. During acetylation, codeine is partially converted to acetylcodeine, but the papaverine and noscapine survive largely unchanged and can be measured in the final heroin product.

UNODC's International Cooperative Group on Drug Dependence (ICGDD) and the European Forensic Institute forensic drug profiling programmes have used alkaloid ratio profiling, combined with stable isotope ratio analysis (13C/12C and D/H ratios by IRMS), to link batches of seized heroin across international supply chains. The 2019 connection of a Mumbai port seizure to a Karachi precursor batch through alkaloid profiling demonstrated the casework utility of this method in Indian transnational investigations.

1. Presumptive colour test
   Apply Marquis reagent (dilute H2SO4 + formaldehyde) to a few milligrams of the exhibit powder. Purple to black confirms opioid class (heroin, morphine, codeine). Document colour change within 30 seconds and at 1 minute. Negative result with Marquis virtually excludes a major opioid.
2. Thin-layer chromatography (TLC)
   Spot exhibit dissolved in methanol on silica gel 60 F254 plate. Develop in CHCl3:MeOH:NH3 (85:14:1). Visualise under UV (254 nm) then with ninhydrin or Dragendorff spray. Diacetylmorphine Rf approximately 0.55 in this system. Resolve from caffeine (Rf ~0.70) and paracetamol (Rf ~0.40).
3. GC-MS confirmation
   Dissolve 1 mg exhibit in methanol, inject 1 µL on Agilent 7890/5977 with HP-5MS column (30 m × 0.25 mm × 0.25 µm). Injector 185°C to minimise diacetylmorphine deacetylation. Oven 100-280°C at 15°C/min. Match retention time and mass spectrum against Cerilliant certified reference standard. Report all co-eluting alkaloids.
4. LC-MS/MS quantification
   Prepare calibration curve from Cerilliant diacetylmorphine standard (1-200 µg/mL). Waters Xevo TQ-S with ACQUITY UPLC BEH C18 column. Multiple reaction monitoring (MRM) transitions: diacetylmorphine 370→211 (quantifier), 370→327 (qualifier). Internal standard: deuterated heroin-d9. Report purity as % w/w diacetylmorphine in the exhibit.
5. Alkaloid ratio profiling (batch linking)
   Quantify morphine, codeine, papaverine, noscapine, and 6-MAM by LC-MS/MS. Calculate codeine:morphine and papaverine:morphine ratios. Compare against UNODC alkaloid database for geographic origin profiling. Document chain of custody across all sub-samples used for profiling to ensure courtroom admissibility of comparison data.

Fentanyl (N-phenyl-N-[1-(2-phenylethyl)piperidin-4-yl]propanamide) was developed by Paul Janssen at Janssen Pharmaceutica in Belgium in 1960 and first used clinically as an anaesthetic induction agent under the trade name Sublimaze. Its analgesic potency is approximately 100 times that of morphine on a weight basis at equivalent receptor occupancy. Commercially, fentanyl is manufactured as patches (Duragesic), lozenges (Actiq), nasal sprays (Lazanda), and injection preparations.

The chemical scaffold has three positions that clandestine chemists have systematically varied to produce the analogue series:

1. The N1-substituent on the piperidine nitrogen (the phenylethyl group in fentanyl): variation here produces acetylfentanyl (acetyl instead of phenylethyl, approximately 15 times morphine potency), butyrylfentanyl (butyryl chain, approximately 7 times morphine potency).
2. The acyl group on the anilide nitrogen (the propionyl group in fentanyl): variation here produces carfentanil (4-carbomethoxy substituent on the piperidine ring, approximately 10,000 times morphine potency), sufentanil (used clinically, approximately 500-1000 times morphine potency).
3. Substituents on the aniline ring: fluorine, methyl, or methoxy groups at ortho, meta, or para positions. Para-fluorofentanyl, 4-chlorofentanyl, and ortho-fluorofentanyl have all been detected in European drug monitoring.

The analogue families detected in the US, UK, and EU between 2014 and 2026:

• Acetylfentanyl: first detected in 2013 US street samples; responsible for overdose clusters in Pittsburgh (2013) and Rhode Island (2016).
• Butyrylfentanyl: detected 2015 US and EU; lower potency than fentanyl but sufficient for overdose at milligram quantities.
• Carfentanil: approximately 10,000 times morphine potency; implicated in the 2002 Moscow theatre hostage crisis where Russian special forces deployed it (combined with other aerosolised agents) through the ventilation system; detected in US street fentanyl in 2016 and in Canadian supplies in 2018.
• Furanylfentanyl (Fu-F): detected in EU in 2016; temporary scheduling by DEA in 2016, permanent Schedule I in 2018.
• Nitazenes: structurally unrelated to fentanyl but pharmacologically similar (benzimidazole opioids); isotonitazene and metonitazene have driven European overdose deaths since 2019 and were emergently controlled by the EU Council in 2021.

The US synthetic opioid overdose crisis divides into three overlapping waves, all of which have analytical chemistry consequences. The CDC's three-wave framework describes the trajectory from prescription opioid deaths (Wave 1, peaking around 2010-2012), through heroin deaths (Wave 2, 2013-2016), to synthetic opioid deaths driven by illicit fentanyl and its analogues (Wave 3, 2016 to present).

Wave 3 began when cartels, principally the Sinaloa Cartel and the Jalisco New Generation Cartel (CJNG), began manufacturing fentanyl in Mexico from precursors sourced primarily from China. The CDC data shows:

• 2013: approximately 3,000 synthetic opioid deaths
• 2016: approximately 19,000 deaths (jump driven by fentanyl appearing in heroin supply)
• 2019: approximately 37,000 deaths
• 2021: approximately 71,000 deaths (pandemic-era surge; increased isolation, fentanyl in stimulant supply)
• 2023: approximately 73,000 deaths (plateau, but fentanyl presence broadening to counterfeit pills)

The analytical consequence at the forensic level is that US laboratories shifted from heroin confirmation (a well-characterised SWGDRUG workflow) to a fentanyl-first detection protocol. Screening now prioritises fentanyl, acetylfentanyl, carfentanil, and the principal nitazene analogues before moving to traditional opioid panels. FTIR-ATR instruments (Bruker Alpha, deployed by DEA and many state labs for rapid field screening of powered exhibits) have been programmed with fentanyl spectral libraries; however, FTIR cannot distinguish fentanyl from acetylfentanyl or carfentanil because their spectra are extremely similar, making GC-MS or LC-HRMS confirmation mandatory before any scheduling opinion.

The rainbow fentanyl phenomenon (DEA intelligence brief, 2022): Sinaloa Cartel-linked supply networks began distributing fentanyl pressed into pills coloured blue, pink, green, and purple. These were found to be intentional marketing to younger users who associate bright-coloured pills with candy. Forensic laboratories confirmed that the colouring agents (food dyes, synthetic pigments) do not interfere with fentanyl identification but complicate presumptive screening with colour-change tests.

In the UK, the EMCDDA and UK Forensic Capability Network have so far documented a different supply dynamic: the UK fentanyl problem as of 2024 involves pharmaceutical fentanyl patch extraction ("patch cooking") as the dominant source, rather than illicit manufactured fentanyl, though intelligence assessments suggest this is changing. In India, the fentanyl problem is primarily one of pharmaceutical diversion from licensed manufacturers and the presence of fentanyl in counterfeit pain formulations, rather than the illicit-manufactured street fentanyl that dominates the US crisis.

The prescription opioid landscape presents a distinct forensic challenge: distinguishing legitimate pharmaceutical product (which may have been diverted but retains its original chemical form) from counterfeit product (which may contain the correct active ingredient at incorrect dose, a substitute opioid, or cutting agents), and from entirely adulterated product that bears the pharmaceutical branding but contains none of the labelled substance.

Tramadol: Tramadol is a centrally acting opioid with a dual mechanism: weak mu-opioid receptor agonism and noradrenaline/serotonin reuptake inhibition. It is the world's most consumed opioid by volume in 2023 (IMS Health/IQVIA data), with India a significant global manufacturer through generics production in Hyderabad and Gujarat. The West African tramadol crisis, extensively documented by UNODC and Interpol's Operation Pangea series, involves tramadol tablets manufactured in India at 225 mg (well above the 50-100 mg therapeutic dose range) and illegally exported to Sahel countries. In India, tramadol is scheduled under Drugs and Cosmetics Rules as a Schedule H1 drug (prescription-only, enhanced record-keeping), not under NDPS, making its diversion analytically detectable (GC-MS or LC-MS/MS confirms identity and quantifies dose) but legally prosecuted differently from NDPS cases.

Oxycodone: A semi-synthetic opioid derived from thebaine (extracted from Papaver bracteatum or from poppy straw). OxyContin (controlled-release oxycodone, Purdue Pharma) was the centrepiece of the US prescription opioid crisis: 2.3 billion OxyContin tablets distributed between 1996 and 2018, with Purdue Pharma's market claim that OxyContin's controlled-release formulation made it less liable to abuse (a claim the company's own research contradicted, as established in the 2021 bankruptcy proceedings). Forensic chemists in US opioid-epidemic casework frequently encounter oxycodone in diverted tablets, crushed powder (extraction of controlled-release formulation), and in counterfeit "M30" blue tablets that the DEA's sampling data shows contain fentanyl in approximately 6 out of 10 tablets seized.

Buprenorphine: A partial mu-opioid agonist and kappa-antagonist, used clinically for opioid use disorder treatment (Suboxone, containing buprenorphine and naloxone) and for pain (Belbuca, Butrans patch). Buprenorphine's forensic significance comes from diversion in two directions: street sale of Suboxone films by patients who obtain them through treatment programmes, and use of diverted buprenorphine as a heroin substitute (the "bupe circuit" documented in European and US harm-reduction research). Under NDPS in India, buprenorphine is a psychotropic substance listed in Schedule II; its dispensing is tightly controlled by the Ministry of Health's guidelines on Opioid Substitution Therapy. Under the US CSA, it is Schedule III. Identification in casework is straightforward by LC-MS/MS (MW 467.6, characteristic MRM transition 468.3→396.2); quantification matters because diverted Suboxone films have a stated dose of 2 mg or 8 mg buprenorphine.

A standard opioid casework analytical workflow in an accredited forensic chemistry laboratory follows SWGDRUG identification tiers and the reporting requirements of the relevant jurisdiction (NDPS, DEA Microgram, or FSR Codes). The workflow is not linear in all cases: the presumptive result may indicate multiple opioid classes, or the exhibit may be a complex mixture that requires a non-standard analytical approach.

The exhibit arrives sealed, with a chain-of-custody document. The forensic examiner records the exhibit condition, mass, and physical description before any analysis. For tablets, the total count and individual tablet mass are documented; a representative sample is taken (typically the ASTM E2520 or UNODC sampling guidance for large seizures), and the remainder is resealed.

The key instrument-level detail for each tier:

• Presumptive tier (colour test): Marquis (H2SO4 + formaldehyde) gives purple-black for heroin, morphine; Mecke (H2SO4 + selenious acid) gives blue-green for morphine, yellow for codeine, which helps differentiate within the opioid class; Scott test (cobalt thiocyanate) is specific for cocaine and does not respond to opioids.
• Category B confirmation (FTIR-ATR, Raman): Bruker Alpha FTIR-ATR with HATR crystal gives a mid-IR spectrum (4000-400 cm-1) that is matched against spectral libraries (SWGDRUG, NIST). Key diacetylmorphine bands: 1730 cm-1 (ester C=O stretch, both acetyl groups), 1665 cm-1 (amide C=O), 1200 cm-1 (C-O-C stretch). Fentanyl: 1631 cm-1 (amide C=O), 698 cm-1 (monosubstituted benzene ring). FTIR cannot distinguish fentanyl analogues reliably due to spectral similarity; this is a critical limitation.
• Category A confirmation (GC-MS): Agilent 7890A/5977B with HP-5MS or DB-5 column. EI mass spectrum of diacetylmorphine: m/z 369 (M+), 327, 310, 268 (base peak in most references), 165. Fentanyl: m/z 336 (M+), 245 (base peak, tropylium-piperidine fragment), 189. Carfentanil: m/z 394 (M+), 303, 245. A difference of 28 mass units (one CO group) separates acetylfentanyl (m/z 322) from fentanyl (m/z 336), easily resolved.
• Quantification: LC-MS/MS with deuterated internal standard. Waters ACQUITY UPLC with Xevo TQ-S. Report as per cent w/w of active substance in the exhibit mixture.

The full six-step workflow is documented below.