Amphetamine use and purity
Amphetamine Consumption Patterns
Amphetamine is a Class B drug which nonetheless shows some features of physical dependence. The main effects are an increase in alertness and tolerance of physical activity Tolerance to the stimulant effects develops rapidly - the main reason why widespread prescribing of the drug for obesity was restricted. A therapeutic dose of 5mg (pure) amphetamine may have the same effect in a novice user as 300mg in a heavily dependent user.
Alverno et al[i] noted in 1975: 'Physical dependence is rarely associated with amphetamine use. However pronounced tolerance develops and the experienced amphetamine abuser may eventually take more than 1g (pure drug) per day.'
In our own IDMU surveys in 1994[ii] and 1984[iii] the heaviest amphetamine users reported spending £300 to £500 per month on the drug in 1994, over £100 per month in 1984 (when average purity was closer to 20% and at a similar price (not allowing for inflation)[iv]. These surveys would under-represent heavier amphetamine users due to the relatively small numbers involved, and most of those who responded to the amphetamine questions in both surveys were occasional or experimental users of the drug. From the IMDU 1997-99 surveys, usage was calculated on the basis of the number of monthly purchases, the quantity purchased, and the percentage claimed for personal use. A total of 770 amphetamine users provided the raw data for these questions (Table 1).
Amphetamine Usage (1999-1997)
Our 2001-05 surveys (n=9929) respondents were asked how much street and base amphetamine they used per week (Table 2), of which 294 provided data for either or both purities. Though the sample was smaller in relation to total respondents, the distribution within the amphetamine users was similar.
Amphetamine Usage (2001-2005)
|Percentile|| Street/wk (g)
|| Base/wk (g)
|| Daily (g)
Continuous daily use is rare, more frequently the drug is taken in extended runs lasting up to several days, where sleep is avoided by frequent use of relatively large amounts, followed by a "crash" where the user sleeps, in some cases for several days, to wake up ravenously hungry and frequently suffering acute depression[v]. This induces another bout of drugtaking thus perpetuating the cycle. During the latter stages of a binge the user may develop paranoid delusions and may present as a psychiatric emergency. This "amphetamine psychosis" may be distinguished from schizophrenia in that the symptoms recede in the absence of the drug.
Klee & Morris[vi] found that 17% of iv. amphetamine users surveyed reported spending more than £150 per week on the drug. This would be equivalent to 10-30 grams (by the gram) or 1.5 to 2 ounces (42-56g) if bought by the ounce. 2% of injectors spend over £300 per week, most probably 3 to 4 ounces (84 to 112g), representing 12-16 grams per day of "street" quality material. Klee & Reid[vii] in a targeted study of 60 amphetamine users in the Greater Manchester area found 42% of respondents consuming more than the mean ~2g per ¬averageÿ day, with 16% consuming over 4g and 2% over 5g per day. One in seven were daily users, most used weekly or more often, 40% had injected and 77% had ¬bingedÿ within the previous six months. Quality was considered very or fairly important by 98% of respondents, users would judge the quality by taste, smell and appearance, and by trying it.
Caplin & Woodward[viii] found that 11% of primary amphetamine users spent more than £200 per week on the drug, with 3% spending over £250. These figures are consistent with those of Klee & Morris above.
Oral or intranasal use is less efficient than intravenous use, but there is no recent published evidence as to the extremes of consumption via these routes of administration. Newcombe[ix] suggested that "ravers" might use half a gram during a night of 6% speed (30mg), about 6 times the therapeutic dose, but well below the dosages reported elsewhere for primary amphetamine users.
Several studies of individuals with amphetamine psychosis have indicated daily dose ranges of the pure drug.
Connell[x] - 500mg to 975mg
Kramer[xi] - 150mg to 2000mg
Abruzzi[xii] - 2000-4000mg
Davis & Schlemmer[xiii] - 100mg to 300mg
Reported dosages from the literature must be qualified by the purity of the amphetamine which was being consumed. Reports from Sweden[xiv], the USA[xv] and Australia[xvi] are not directly comparable as the markets in these countries are different, and the purities and prices vary markedly. Daily intravenous use of up to 1500mg (1.5g) of pharmaceutical amphetamine was reported in the 1960s[xvii], equivalent to 30 grams of 5% powder. Clearly, use of such quantities of low-quality powder would be unrealistic, and intravenous use of such material[xviii][xix] would entail severe health risks from the contaminants, although oral consumption of up to 8 grams per day is reported by ISDD[xx]. Heavier amphetamine users are thus more likely to seek higher purity amphetamine powder, commonly (but inaccurately) known as 'base'.
Given the low purity of most street powders, larger quantities of street amphetamine powder are required to produce the desired effect. A typical 'recreational' dose of 50mg pure drug would require 1g of 5% powder, or 5 grams of 1% powder. A heavily tolerant and dependent user seeking to consume 600mg of pure amphetamine per day a person would need to use 12 grams of 5% amphetamine powder, 6 grams of 10%, or 3 grams of 20% powder.
Purities of Amphetamine Samples
A study[xxi] of drug content of powders examined in detail the purity of amphetamine seizures made by Police and by Customs & Excise between January and August 1992. The purity of seizures were plotted against the amount seized. Average purity of amphetamines seized by police was 5.1%, with Customs seizures averaging 43.7%. In neither sample was a relationship found between the amount seized and the purity. There were seizures of 10kg with 3% and 4%, and a seizure of a few grams with 16% amphetamine.
Home Office statistics[xxii] chart the changes in amphetamine purity over the past 10 years (fig 1). During the early 1990s the average purity was typically 5-6%, which rose steadily to 15-18% during 1998-99. Following successful police action against a large manufacturing syndicate the availability and purity of amphetamine fell back to 5-8% from late 1999 to mid 2001, although by late 2001 the average had risen above 10% once more. This ¬amphetamine droughtÿ coincided with a substantial increase in usage of cocaine and crack.
The range of amphetamine purities analysed by the Forensic Science Service during 1997 were given in a Home Office written answer in April 1998 and are reproduced in table 3 below.
Amphetamine Purities 1997
|Purity||% of Cases
|Less than 5%
|More than 70%
|Police mean 14%
||police mode 5%
||approx 40% purity
A report of purities of amphetamine samples analysed by the Wetherby laboratory[xxv] (covering Yorkshire, Humberside & North East England found amphetamine purities of samples analysed during the period January-June 1995 averaged 7.8%, and from July to December 1995 the report indicates an average purity of 10%, with most street samples in the range 1%-9%, with the most common cutting agents being glucose, with caffeine and ephedrine often present. The average wrap size was 646mg (no range given).
It is apparent from these figures that the common assumption that amphetamine would be cut to levels of 5% or less are outdated, representing less than median purity, and that a substantial proportion of amphetamine on the UK market is sold at higher purities - 41% of seizures were found to be over 10% purity in 1997.
The average wrap size analysed by the Wetherby laboratory[xxvi] was 616mg in January-June and 646mg in July-December 1995 (no range given). Analysed wraps will tend to underestimate the sizes of wraps sold on the street, as partially used wraps may be seized and analysed, and these will tend to depress the average. The analysed average of seized wraps would thus fall somewhere between 50% and 100% of the actual average wrap size when sold. Analysed wrap sizes would therefore be consistent with an actual wrap size (when sold) of approximately one gram.
Preliminary results from the 1995-97 series surveys[xxvii] indicate purchase quantities of amphetamine to range from one gram wraps to over 100g, with 1/8oz (3.5g) at £15-£25 being the average purchase among regular amphetamine users.