Sir, - I am afraid I must disagree with David Carroll (November 19th), who criticises your report of November 14th for describing the morning-after pill as a contraceptive and not an abortifacient.
Mr Carroll outlines an over-simplified and factually inaccurate mechanism of action. He claims that the pill causes "the uterus to shed its lining, thus preventing the implantation of any such [fertilised] egg, or indeed causing its expulsion if it has implanted already." According to the manufacturers, Schering Health Care, Levonelle-2 (the morning after pill approved by the Irish Medicines Board for licensing) has two possible mechanisms of action depending on the stage of the woman's cycle.
1. If Levonelle-2 is taken in the preovulatory phase (the egg has not yet been released by the ovary) it will prevent ovulation. Therefore fertilisation can not take place.
2. If Levonelle-2 is taken after the egg has been released and fertilisation has taken place, it will cause changes to the uterus lining that will discourage implantation. These are subtle enzymatic changes - not, as Mr Carroll claims, shedding of the uterus lining.
And, again contrary to Mr Carroll╣s claims, Levonelle-2 is not effective once the process of implantation has begun. It is for this reason that Levonelle-2 must be taken within 72 hours of intercourse.
It seems absurd to describe a drug that has no known effect on an implanted fertilised egg, let alone on a developing foetus, as an abortifacient.
In his letter Mr Carroll asks The Irish Times for balance and transparency with its journalism. Perhaps Mr Carroll could be more balanced and transparent when writing about such a sensitive issue. - Yours, etc.,
Andrew Legge MPSI, Ceant Fort, Dublin 8.