AIM-listed TyraTech slumped after warning that revenue for the current year is now expected to come in below market expectations due to a decision by certain new retailers in the US to delay the review of its Vamousse treatment product.Revenue is expected to come in at $4.8m, up from $1.4 last year, but below expectations of $6m.The group explained that some new retailers have delayed a review of Vamousse, which is the second best-selling head lice brand at Walmart, from the end of 2014 until the early part of 2015 "in order to better conform to their internal line review schedule and ensure maximum impact for the launch".Revenue from product sales is expected to rise from zero to $2.8m, while net losses for the year are expected to total $4.8m, down from $4.9m.Chief executive Bruno Jactel said: "TyraTech has introduced ten new products to the market in 2014 in both the US and the UK, securing listings and partner relationships with a number of well-known retailers and generating substantial revenue growth."In addition, the company has a strong and growing pipeline of new products. These achievements have been made possible by the continuous support of our employees and shareholders, and now our customers. We firmly believe the company has strong growth potential and that the foundations are in place to realise significant future value."The group's share price had fallen 20.74% to 4.26p by 10:28.