E-DRUG: Norgestrel and combined contraceptive pills (cont'd)

[John Urquhart <urquhart@netcom.com>]

E-drug: Norgestrel and combined contraceptive pills (cont'd)
---------------------------------------------

I didn't mean to imply that it was the single optical isomer that made
NORPLANT so effective, for clearly it is the assured continuity of drug
exposure that a well-designed drug delivery system can provide. In
contrast, daily dosing with the norgestrel-only 'minipill' requires
exceptionally punctual dosing, because, as McCann and Potter point out
in their authoritative review on progestin-only contraception (McCann
MF, Potter LS. Progestin-only oral contraception: a comprehensive
review. Contraception 50 (suppl 1), S9-S195, 1994), the duration of
action of each dose averages about 27 hours, which gives only an hour
or two margin for error in dose-timing to maintain continuity of drug
action. Studies during the past decade with electronic monitoring of
ambulatory patients' dosing indicate that only about 15% of patients
are consistently punctual to within those limits, so patients selected
from that punctual minority could probably get good contraception
from the 'minipill', provided they didn't have difficulties with the
mid-cycle spotting that often occurs with that method.

The contrasting effectiveness of the oral and the delivery systems
forms of progestin-only contraception are analyzed in my recent
review, "Can delivery systems deliver value in the new pharmaceutical
marketplace?" Brit J Clin Pharmacol 44: 413-419, 1997. 

John Urquhart
Prof. of Pharmaco-epidemiology
Maastricht University
Maastricht NL
urquhart@netcom.com
  
--
Send mail for the `E-Drug' conference to `e-drug@usa.healthnet.org'.
Mail administrative requests to `majordomo@usa.healthnet.org'.
For additional assistance, send mail to:  `owner-e-drug@usa.healthnet.org'.