• Chemical diversion;
  • ephedrine;
  • illicit drug;
  • methamphetamine;
  • precursor;
  • pseudoephedrine

Methamphetamine is a growing global problem. In 2007 the United Nations estimated that around 25 million people use methamphetamine or related amphetamine derivatives each year [1]. The production of methamphetamine is difficult to control because it can be made from chemicals that are contained in everyday products, ranging from cleaning fluids to medications [2]. Policing supply involves balancing the need for these chemicals to be available for legitimate purposes while preventing their diversion into clandestine drug manufacture.

Preventing this so-called ‘chemical diversion’ has been at the forefront of tackling methamphetamine supply for decades. In 1988 member states of the United Nations agreed to regulate precursor chemicals used in illicit synthetic drug manufacture [3]. The majority of subsequent precursor diversion initiatives have targeted ephedrine and pseudoephedrine as chemicals that convert readily to methamphetamine, and which are widely available as decongestant medications [4]. These regulatory measures focused initially on bulk precursor diversion from industry, and imposing tight regulations on consumer pharmaceuticals containing ephedrine. More recent efforts have focused on preventing the diversion of over-the-counter (OTC) cold and flu remedies containing pseudoephedrine [5–7].

The tightening of these regulations in some countries has effectively placed pseudoephedrine-containing medications behind the counter: a deterrent to both criminals and people with a legitimate need for decongestant medication. To circumvent this inconvenience, pharmaceutical companies have introduced OTC products containing a closely related decongestant compound, phenylephrine (PE). PE is a convenient substitute for pseudoephedrine that is already approved for pharmaceutical use [8]. However, the limited evidence available suggests that PE is ineffective at the currently approved dose [9,10]. While higher doses may be safe and effective, further trials would be needed to confirm whether this is the case [10].

It is also not clear whether using PE in OTC medications will have an impact on methamphetamine supply. It is often assumed that PE cannot be converted to methamphetamine [11,12], but the evidence supporting this claim is not well documented. Rather, existing evidence suggests that converting PE to methamphetamine is more difficult than current ‘home-bake recipes’ using pseudoephedrine [13], and that PE is not used currently in clandestine methamphetamine manufacture. Given the increasing sophistication of synthetic drug manufacture [1] and the increased availability of related information on the internet [14,15], it may not be long before ‘recipes’ emerge for the conversion of PE to methamphetamine.

Even if converting PE to methamphetamine proves too taxing for clandestine chemists, they would still have several manufacturing options at their disposal, such as using different precursor chemicals or manufacturing their own precursors [2,14,15]. Precursor chemicals could also be trafficked illegally from countries where they are poorly regulated, or drug manufacturing operations could be relocated to these countries. This trend is already evident in the Asia Pacific region, where the illegal trafficking of precursor chemicals has become a lucrative criminal enterprise in its own right [7], and the detection of large-scale methamphetamine laboratories in the absence of sizeable local markets for the drug [16] suggests that production is destined for neighbouring consumer countries. Trafficking of the drug to consumer markets may be high-risk, but if the cost of production is sufficiently low, importation could still be viable (cf. cocaine importation into the United States).

While these limitations render precursor control an incomplete guard against illicit synthetic drug supply, law enforcement's ability to effectively ‘tax’ the illicit drug market by reducing the availability and increasing the cost of precursor chemicals has a downstream impact on the illicit drug market. Several shifts in precursor regulation within the United States have produced significant, albeit transitory, reductions in both methamphetamine-related hospital admissions and arrests [5,6]. While positive, further work is needed to appreciate the complexity of the drug market response to precursor regulations, and the medium- to long-term costs and benefits associated with their implementation [17].

Successful precursor regulation may also have unintended consequences which need to be anticipated and managed. As regulation of precursor chemicals in wealthy destination markets becomes more stringent, responsibility for policing chemical diversion and synthetic drug manufacture and managing harms from synthetic drug use are likely to shift increasingly to developing countries—many of which have limited capacity to manage such problems. Reductions in the domestic production of methamphetamine in some countries may also lead to increased importation of the drug to these countries, more organized criminal involvement in the drug market and shifts toward the trafficking and use of substitute drugs. All these hypothetical shifts in the drug market could alter the relative availability of various drugs in different geographic regions, the purity of these drugs, the way in which they are used and the consequent harms from drug use at a global level.

Overcoming reactive shifts in the methamphetamine market will require making precursor legislations consistent both within and across countries and adopting a strategic approach that considers the various options open to illicit drug manufacturers, rather than reactively targeting current trends in manufacture. Of particular importance, tightening domestic precursor regulation needs to be coupled with improving the capacity of developing countries to regulate precursor chemicals, and strengthening border controls to guard against precursors being trafficked illegally between countries. Such measures have already been initiated in some regions (e.g. the Asian Collaborative Group on Local Precursor Control and the Pacific Precursor Working Group), although their impact has yet to be determined.

Our current weakness is that many of our expectations about precursor regulation are based on speculation rather than evidence. Even the most rudimentary statistics on precursor movement (both licit and illicit) are incomplete or unavailable in many countries. Coupled with a dearth of quantitative data on the dynamics of illicit drug markets, we can make only a calculated guess at the impact of any given precursor control measure. In order to overcome this problem, we need to embark on a serious quantitative analysis of the dynamics of illicit drug markets (e.g. cost of production, price elasticity of drugs against availability and their potential for substitution) and how they respond to various interventions.

Aside from understanding the impact of precursor regulation on methamphetamine use, a broader challenge is to appreciate whether successfully controlling methamphetamine supply will reduce overall problems from drug use. In theory, lower availability of a drug should reduce its use, and therefore the number of people at risk of transgressing into problem drug use [18]. In the real world, drugs users have a habit of shifting from one drug to another depending on availability and cost [19]. Although this substitution is unlikely to be complete, and the net harms from drug use may fall, we currently lack the empirical evidence to anticipate whether interventions will result in an overall reduction in drug-related harm. Indeed, some drug market shifts may not only increase the level of harm, but they may also require a capacity shift within the drug and alcohol sector. A clear example of this can been seen following shifts between stimulant and opioid use, where the dominant harm moves from psychiatric complications to fatal overdose, and markedly different treatment and prevention approaches are required. For this reason, the relative harms associated with such drug market shifts need to be monitored carefully so that we can determine which drug control interventions have the most desirable public health outcomes.


  1. Top of page
  2. Acknowledgements
  3. References

The author wishes to acknowledge the National Drug Law Enforcement Research Fund for funding of earlier related research on methamphetamine supply, the reviewers of this editorial and Shane Darke for their helpful comments, and the following people for their explanations of precursor chemical regulations: Paul Willingham, Vincent Murtagh, Robert Rushby and Robert Taylor.


  1. Top of page
  2. Acknowledgements
  3. References