December 4, 2003

News Release: Sontra Completes Promising Phase 3 Clinical Study

Sontra Medical Corporation (Nasdaq SC: SONT) announced today the completion of a Phase 3 clinical study demonstrating that skin anesthesia from topical 4% lidocaine was achieved in five minutes following treatment with the Company's SonoPrep skin permeation device. SonoPrep applies low frequency ultrasound to the skin to create imperceptible, reversible micro-channels through the stratum corneum thereby making the skin permeable to transdermal and topically applied drugs. In this study, pain was evaluated in patients undergoing intravenous (IV) cathetherization in the emergency room. The research team treated the skin of patients with the SonoPrep for approximately 15 seconds and then applied 4% topical lidocaine to the permeated skin site. After a five minute waiting period the IV catheters were inserted. The principal investigator for this study was Dr Bruce Becker, Attending Physician at the Department of Emergency Medicine, Rhode Island Hospital and Assistant Professor at Brown University. 'This study demonstrated that skin anesthesia from topically applied lidocaine was achieved in five minutes with the use of SonoPrep'stated Dr. Becker. 'Since the existing topical lidocaine products require a thirty to sixty minute waiting period to achieve effective skin anesthesia, they are rarely used before IV's and needles are inserted, even though these procedures are often very painful. Clinicians will be able to use SonoPrep to achieve rapid skin anesthesia. This intervention will be especially important for chronically ill children and adults who must endure repeated needle sticks and IV therapy.'

'The data from this Phase 3 clinical study clearly demonstrates that our SonoPrep skin permeation technology improves the clinical utility of topical lidocaine products,'stated Thomas W. Davison, Ph.D., Sontra's President and Chief Executive Officer. 'Before the end of December, Sontra will initiate a 320 patient study that the FDA requested we complete before submitting a 510(k) for market clearance. We expect to complete this study in the first quarter of 2004 and assuming FDA 510(k) clearance we are scheduled to launch SonoPrep and our topical lidocaine procedure tray into the $100 million topical anesthetic market during the second quarter of 2004.'

About Sontra Medical Corporation (www.sontra.com)

Sontra Medical Corporation is the pioneer of SonoPrep, a non-invasive ultrasound-mediated skin permeation technology that enables transdermal diagnosis and drug delivery. Sontra's products under development include: the Symphony Diabetes Management System for continuous non-invasive glucose monitoring that is being co-developed with Bayer Diagnostics; a rapid onset (less than 5 minutes) topical anesthetic delivery system and the use of SonoPrep for the transdermal delivery of large molecule drugs and biopharmaceuticals.

This press release contains forward-looking statements, which address a variety of subjects including, for example, the expected benefits and commercialization of the SonoPrep device and technology, and the expected timing of the commercial availability of the SonoPrep device and lidocaine procedure tray. Statements that are not historical facts, including statements about our beliefs and expectations, are forward-looking statements. Such statements are based on our current expectations and are subject to a number of factors and uncertainties, which could cause actual results to differ materially from those described in the forward-looking statements. The following important factors and uncertainties, among others, could cause actual results to differ materially from those described in these forward- looking statements: adverse results in product development, clinical trials and commercialization efforts; failure to obtain and maintain patent protection for discoveries; commercial limitations imposed by patents owned or controlled by third parties; dependence upon strategic partners to develop and commercialize products based on our work; difficulties or delays in obtaining regulatory approvals to market products resulting from development efforts; the commercial success of products; and the requirement for substantial funding to conduct research and development and to expand commercialization activities. For detailed information about factors that could cause actual results to differ materially from those described in the forward-looking statements, please refer to Sontra's filings with the Securities and Exchange Commission, including Sontra's most recent Quarterly Report on Form 10-QSB. Forward-looking statements represent management's current expectations and are inherently uncertain. We do not undertake any obligation to update forward- looking statements made by us.

Contact: Sean Moran, CFO Sontra Medical Corporation (Tel):508-553-8850, ext 234

SOURCE Sontra Medical Corporation

Sean Moran, CFO, of Sontra Medical Corporation, +1-508-553-8850, ext. 234

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