The move could force pharmaceutical companies into a reformulation drive to produce alternative over the counter (OTC) cold and flu products that do not contain the restricted ingredients.
The MHRA has issued a public consultation letter seeking opinion on the proposed restrictions, which would see the nasal decongestants converted to prescription-only and a reduction in pack size by the end of 2007.
The move comes in response to the growing illicit use of OTC ephedrine- and pseudoephedrine-based drugs for the production of the Class A controlled drug, methylamphetamine.
The agency highlights the fact that alternative active ingredients can be used in cough/cold remedies, noting that "many manufacturers of pseudoephedrine/ephedrine containing products already have phenylephrine containing products authorised and many are currently available with similar indications."
However, experience in the US, where sales of pseudoephedrine were restricted last year, has shown some difficulties in making a straight swap from pseudoephedrine to phenylephrine, with some companies even dropping development of such products as unfeasible.
Phenylephrine has some distinct disadvantages compared to pseudoephedrine, which have hampered the growth of a market that was anticipated to expand rapidly in the US in the face of the new legislation.
Phenylephrine does not last as long in the body as pseudoephedrine, which can make it a less attractive option for consumers, and some parties have questioned its efficacy altogether.
Only last month, US firm SCOLR dropped its phenylephrine development plans, claiming that the treatment "did not justify continued internal development."
SCOLR vice president and chief technology officer, Stephen Turner, told In-PharmaTechnologist at the time that "phenylephrine-based reformulations have not yielded a successful, cost-effective alternative to extended-release pseudoephedrine-based products nor have the new immediate release phenylephrine-based products become popular as replacements for pseudoephedrine."
Despite this, Pfizer, Johnson & Johnson, Wyeth and GlaxoSmithKline now all offer phenylephrine-based cold and flu remedies in addition to their pseudoephedrine products in an effort to maintain an OTC presence.
The MHRA's favoured course of action, based on recommendations from the Commission on Human Medicines (CHM), is to change the legal status of pseudoephedrine-/ephedrine-containing products to prescription-only by the end of the year.
The pack reduction would restrict the maximum pack size to 720mg pseudoephedrine/ephedrine (12 x 60mg tablets or 24 x 30mg in a combination pack or equivalent in other formulations).
The plans also recommend strategies to maintain consumer access to alternative OTC treatments, such as those containing phenylephrine.
The MHRA notes that some manufacturers will need to consider reformulation to expand their product offering in the face of the proposed regulations, but claims that "planned changes over a transition period would…enable costs to be minimised as companies adjust their manufacturing schedules to reduce stock of [OTC] pseudoephedrine/ephedrine products…in order to avoid wastage of stock."
The restriction in pack size, which would completely remove large packs from the market, would also require repackaging schemes on the part of manufacturers.
However, the MHRA maintains that interim measures would be agreed between marketing authorisation holders and the agency so that disruption is minimised; for example, the use of adhesive over-labels so as to avoid destroying existing stock.
By implementing the proposed regulations, the UK would be following in the footsteps of several other countries that have already restricted the sale of drugs containing pseudoephedrine in the face of the growing methylamphetamine problem.
Over the last year, Australia, the US and the Philippines have all taken steps to expressly strengthen controls over preparations containing pseudoephedrine and ephedrine, according to a report published by the International Narcotics Control Board published this month.
The report, responsible for prompting the move on pseudoephedrine by the MHRA, called on all governments to tackle what it calls the "global problem [of]…the diversion of precursors used in illicit manufacture of methylamphetamine," noting that since the beginning of 2005, 30 cases of attempted diversion have been reported to the board.