Effect of acids on heroin

Laboratory study of the effects of citric and ascorbic acids on injections prepared with brown heroin

Jenny Scott*1 BSc, MRPharmS,
Arthur Winfield2 BPharm, PhD, MRPharmS,
Emily Kennedy3 BSc, PhD, MRPharmS, and
Christine Bond4 BPharm, MEd, PhD, MRPharmS.

*Corresponding author.
1.Department of Pharmacy and Pharmacology, University of Bath, Bath, BA2 7AY,
UK. email: prsjs@bath.ac.uk
2.School of Pharmacy, University of Kuwait, Kuwait. 3.Boots the Chemists Ltd, UK.
4.Department of General Practice and Primary Care, University of Aberdeen, UK.

The work presented in this paper was undertaken by J.Scott as part of a PhD project. The other authors are supervisors to this project. This paper was written by J.Scott, who's opinions are expressed herein. The other authors reviewed the paper for scientific content and clarity.

KEYWORDS: citric acid, ascorbic acid, brown heroin, purity.

This paper is reproduced by the first author from a paper published in the International Journal of Drug Policy 11(6): 417-422.

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ABSTRACT

The addition of acidic substances to brown street heroin to facilitate the solubility of diamorphine in the injection preparation process is commonplace amongst UK injectors. Knowledge of the chemistry behind this process supports the need for this stage in the injection preparation process. It is currently illegal, under the Misuse of Drugs Act, section 9A, to supply acidifiers and other paraphernalia to injectors in the UK. In the current climate of evidence-based practice, any consideration given to changing the law would look for evidence to illustrate that the paraphernalia was necessary. Although the theory behind the use of acidifiers suggests they are essential, no work using street heroin has actually been reported to illustrate this fact. Anecdotal information has found some drug users being told by service providers that the addition of acids is unnecessary. The provision of inaccurate information in one area may lead to a lack of trust of all information provided, so it is important that drugs services give credible information to their clients. The small study reported here investigated under controlled laboratory conditions, the effects citric acid and ascorbic acid (vitamin C) on injections prepared with brown heroin, simply to demonstrate the need for acidifiers in the injection preparation process.

Keywords: citric, ascorbic, vitamin C, brown heroin.

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INTRODUCTION

In the UK, 'street' heroin is commonly of the type referred to as 'brown heroin'. Analytical studies have shown brown heroin to frequently contain diamorphine (the main psychoactive drug in heroin) present in the chemical form referred to as basic (Kaa, 1991, Chaudron-Thozet, 1991). Basic diamorphine has a solubility of 1 in 1700 parts of water (Moffat, 1986), which means that very little will dissolve when mixed with small amounts of water alone. When injecting drug users (IDUs) prepare injections with brown heroin, they are known to add acids such as citric acid or ascorbic acid (vitamin C) and heat the heroin in water on a metal spoon to convert the base heroin to a more soluble form (Derricott et al, 1999). i.e.

diamorphine base + citric acid => diamorphine citrate

Anecdotal observations of the researcher and others have found some drugs workers to be informing clients that the addition of acids is unnecessary and the same effects can be achieved by heating the mixture for longer. The chemistry behind the addition of acids to heroin suggests this not to be the case. Without the addition of the acid the chemical complex between the diamorphine and the acid would not be able to happen. However, a search of the literature found that this had never actually been reported from work using real street heroin.

In the UK it is against the Misuse of Drugs Act (section 9a) to supply injecting paraphernalia to IDUs. Included in this is the supply of acidifiers. Although the chemistry behind their use suggests they are necessary, evidence of their effects from laboratory experiments using brown street heroin was considered useful, to support those health authorities and drugs agencies who are applying for exemption from prosecution to enable them to distribute paraphernalia to IDUs as part of their harm reduction schemes.

This paper reports the results of a small laboratory investigation into the effects of citric and ascorbic acid on injections prepared with street heroin. The injection preparation process used in the laboratory was based on safer injecting information and information gathered from heroin injectors, using semi-structured interviews (n = 19). The interview methods and results are not reported in this paper, but are available from the corresponding author. Small quantities of acids, as recommended in safer injecting leaflets were used and their effects on the heroin investigated. The quantities were then varied to illustrate the effect of this.

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METHODS

Following permission from the UK Home Office, the Crown Office for Scotland and the Procurator Fiscal for Grampian, seized samples of brown heroin were obtained from the local police forensic laboratory. The percentage content of diamorphine was established. The amount of heroin used in the experiments was 250 mg, which was based on the most commonly used quantity reported by the IDUs who were interviewed, described as 'a quarter gram'1.. Difficulty arose in establishing whether Oa quarter gram¹ as purchased from a dealer was actually 250 mg in weight. Information from the police on quantities of seized drugs suggested that the weight of a wrap considered to be for personal use varied greatly with maximum weights seen being around 330 mg. Therefore, since 250 mg was within the range of the seized wraps, this quantity was used. The quantity and purity of the heroin used by IDUs will of course vary. Citric acid and ascorbic acid were chosen for investigation are they are known to be used by IDUs (Derricott et al, 1999) and were reported as being used by the interviewed IDUs. To establish a weight for 'a small pinch', as recommended in the safer injecting leaflets, ten small pinches of citric acid were weighed and the average weight taken. Equal weight of ascorbic acid was used to allow the two results to be compared.

1. One gram contains 1000 milligramms (mg)

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All factors used in the preparation process had to be measurable, so they could be kept constant, to allow comparison of the results. The process used is shown in figure 1. The stages in the preparation process were identified from safer injecting advice (Exeter Drugs Project, 1991, HIT, 1995) and the information gathered from the IDUs interviewed. The quantities used were based on information gathered from the IDUs. The end-point for the heating was described by the interviewees as being when the mixture began to bubble and the clear liquid separated from the undissolved material. The process factors such as the height of the spoon base from the flame, temperature of water added and length of time of heating were measured for the first injection prepared and kept constant.

Figure 1: Stages in the heroin preparation process simulated in the laboratory

The amount of diamorphine in the resulting injections was measured using an analytical process known as Capillary Zone Electrophoresis (CZE). Details of this equipment, the analytical materials used and the laboratory techniques are given in appendix 1 of this paper. The quantities of citric and ascorbic acids were also varied to illustrate the effect this had on the amount of diamorphine in the resulting injections. The amounts used were approximate multiples of the weight used to represent one Osmall pinch¹. The injections were filtered with a piece of filter from an unsmoked cigarette. Each injection was analysed three times and the average results used to calculate the amount of diamorphine in the injection. Each quantity of acid was tested three times and the average diamorphine content in the three injections calculated. An injection was also prepared without the addition of acid.

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RESULTS

The diamorphine content of the heroin was found to be 56 %.

Ten small pinches of citric acid were weighed and the average weight found to be 15 mg. Approximate multiples of this quantity which were also investigated were 7 mg ('half a pinch'), 3 mg ('a quarter a pinch') and 30 mg ('two pinches'). The ascorbic acid was restricted to two quantities due to the limited amount of heroin available. These quantities were 15 mg and 60 mg.

Figure 2 shows the effects of varying the quantity and type of acid in the preparation of heroin injections.

Figure 2: Effect of quantity and type of acid on amount of heroin in injections

The injection prepared without the addition of acid could not be filtered, as the solid heroin did not dissolve in the water. Attempts to filter it were unsuccessful. Instead a precipitating effect was seen.

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DISCUSSION

Figure 2 illustrates how, as expected, the quantity of diamorphine in the resulting injections increased as the quantity of citric acid increased. The inability to produce an injection when no acid was added, coupled with the data in figure 2, supports the chemistry that shows that the addition of acidifiers is a necessary stage in the injection preparation process used by IDUs. Therefore, advising that the addition of acid is unnecessary is incorrect.

Different purities of heroin will require the additons of different amounts of acid. Concerns around tissue and vein damage from the use of too much acid have led to safer injecting advice telling IDUs to use as small quantities as possible, which seems vague. This leads to the question of whether more accurate information can be given on the quantities of acidifers required. The diamorphine content in the herion used for this work was found to be 56%, which means 140 mg of diamorphine was present in the 250 mg quantities used. The question of how much acid would be needed to dissolve all this diamorphine can be addressed using chemistry calculations. Chemicals are compared by using a term called 'moles'. One mole of any chemical contains the same number of molecules, although the weight of one mole will vary between chemicals as the molecules have different sizes of structures. Based on chemical values known as pKa, it is known that for every mole of diamorphine base, a third of a mole of citric acid is needed to completely convert the diamorphine to the soluble citrate form. For ascorbic acid, the pKa values tells us that for every mole of diamorphine base one mole of ascorbic acid is needed. In weight terms a mole of diamorphine base weighs 369.4g, a mole of citric acid weighs 192.1g and a mole of ascorbic acid weighs 176.1g. Therefore for every 369.4g of diamorphine base, 64.03g of citric acid or 176.1g of ascorbic acid would be needed to completely convert the base to a soluble salt. When this calculation is performed using the 140mg of diamorphine base that was in each 250mg quantity of heroin, it can be calculated that the amount of citric acid needed to fully dissolve all the diamorphine would be 24.3 mg. For ascorbic acid the quantity would be 67 mg. From fig. 2 it can be seen that for the 30 mg of citric acid experiments and 60 mg of ascorbic acid experiments, which used quantities close to these amounts, the amount of diamorphine in the prepared injections was not close to 140 mg. In order to establish where the diamorphine may have been lost, various parts of the preparation process were tested. Diamorphine was detected in the filters, on the tip of the needle sheath used to stir the mixture, in the residue left on the spoon after preparation and in the vapour which evaporated from the spoon on heating. Although not investigated, the last point suggests that heating the mixture for longer would only serve to evapourate more of the diamorphine.

Without a knowledge of the amount of diamorphine in heroin, IDUs cannot be accurately advised on the quantity of acid needed. If the purity of the diamorphine could be determined, for example through providing a testing facility, accurate calculations could be made, allowing the amount of diamorphine injected to be controlled. This may be considered a harm reduction intervention as records could be kept on the 'dose' used an individual uses and the risk of overdose from unexpectedly high amounts of diamorphine in street heroin could be reduced. However, it may also be viewed as helping people to inject and too radical for contemplation. The issue of providing testing facilities for heroin users is a matter open for debate.

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CONCLUSIONS

These experiments illustrate the point that injecting drug users do need to add acidifiers to heroin that contains diamorphine base, mostly brown heroin, in order to dissolve the drug. Telling drug users that acids are not necessary is false information and telling them to heat the heroin mixture for longer is likely only to increase the loss of drug during preparation. An amendment to section 9a of the Misuse of Drugs Act, as currently proposed by the Home Office (http://www.drugs.gov.uk/ -release date 18.11.02 consultation closes 14.02.03), would allow the legal supply of acidifiers and other paraphernalia to injectors in the UK.

The quantity of acidifier required will vary depending on the acid used and the purity of the heroin, a factor that is not known exactly. Therefore the judgement of the IDU will be the only factor that can determine an approximate amount of acid needed. This opens the debate for the provision of drug testing facilities for heroin users. A knowledge of the diamorphine content in a sample of street heroin and confirmation of it¹s presence in the base form, would allow calculation of the amount of acid needed to dissolve the heroin. This could avoid the use of excessive amounts of acid, which may potentially have long-term health benefits in reducing vein damage.

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REFERENCES

CHAUDRON-THOZET, H., GIRARD, J., and DAVID, J.J., 1992. Analysis of Heroin Seized in France. Bull. Narc, XLIV(1).

DERRICOTT, J., PRESTON, A., and HUNT, N., 1999. The Safer Injecting Briefing. Liverpool: HIT.

EXETER DRUGS PROJECT, 1992. What Works? 2nd ed. (booklet). Exeter.

HIT, 1995. A Guide to Safer Injecting. (booklet). Liverpool: HIT.

KAA, E., 1991. Street Drugs in Denmark. J. Forensic Sci., 36(3), 866-879.

RUNCIMEN, Viscountess., 2000. Drugs and the Law: Report of the Independent Inquiry into the Misuse of Drugs Act 1971. London: The Police Foundation.

MOFFAT, A.C., 1986. (Ed). Clarke¹s Isolation and Identification of Drugs in Pharmaceuticals, Body Fluids and Post Mortem Materials, 2nd Ed. London: The Pharmaceutical Press.

TAYLOR, R. B., LOW, A. S, and REID, R. G,. 1996. Determination of Opiates in Urine by Capillary Electrophoresis. J. Chromatogr. B: Biomedical Applications. 675: 213-223.

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APPENDIX 1

ANALYSIS EQUIPMENT

The analysis technique used was that described by Taylor et al, 1996, using a detection wavelength of 220 nm. The CZE analysis equipment was made by ISCO, model 3850. The capillary was of unmodified silica, 50 µm in diameter and 60 cm long. It was made by Lincoln ISCO, Quality CE. The data was recorded on an ABB Servogor SE120 chart recorder. Validation showed the method used to give a linear response over the concentration range of interest.

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MATERIALS

Citric acid B.P (Thornton & Ross, Huddersfield, UK) and ascorbic acid B.P (vitamin C powder, Boots the Chemists, Nottingham, UK). The standard reference materials, diamorphine (DM Wood, Aberdeen, UK) and levallorphan (Sigma, Poole, UK) were both of pharmaceutical grade. The methanol (Ratheburn, Walkerburn, Scotland, UK) was of HPLC grade and the water was prepared in house to HPLC grade using the Millipore Milli-Q system. The cigarette filters were prepared by removing the filter from an unsmoked cigarette (Lambert and Butler, UK) and dividing it in four. One segment was used per injection. The insulin syringes used were 1 ml capacity (B-D, Oxford, UK).

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EXPERIMENTAL PROCEDURE

Results from the analysis of a solution of diamorphine of known concentration (9.3 µg ml-1) were established and used to allow the amount of diamorphine in the injections to be calculated. The levallorphan was used as an internal standard for the following reason. The analysis equipment produced output data in the form of peaks which represented the detected drugs. However, the height of these peaks with a given concentration of drug was shown by Taylor et al (ibid.) to vary with each analysis run. However, if two drugs are analysed, the ratio between the height of two peaks will not however vary. Levallorphan (10.2 µg ml-1) was used as the second drug against which the peak height ratio was calculated. The ratios were calculated from the analysis of the solutions of known concentration and the ratio between the peak of the unknown concentration (the injections prepared with heroin) and the levallorphan were compared to calculate the concentration of diamorphine in the injections.

The injections were prepared as described in figure 1 of the main text. As they were too strong to analyse 'neat', they were diluted by the addition of enough methanol to give 100 ml solution. 1 ml of this solution and 1 ml of the levallorphan standard solution were mixed and made up to 10 mls with water. This solution was then analyzed immediately and the dilution accounted for in the calculations.