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Dr. Bob is Robert Hsiung, MD,
bob@dr-bob.orgShown: posts 1 to 4 of 4. This is the beginning of the thread.
Posted by Kimbersaur on August 14, 2005, at 17:18:13
I've read that Lamictal can decrease the effect of oral contraceptives, and I was wondering if anyone knows how common it is and if there are certain contraceptives that it doesnt interact with. Any ideas?
Posted by ed_uk on August 15, 2005, at 4:55:23
In reply to Lamictal and oral contraceptives, posted by Kimbersaur on August 14, 2005, at 17:18:13
'Interactions involving Oral Contraceptives
Effect of oral contraceptives on lamotrigine:
Systemic lamotrigine concentrations are approximately halved during co-administration of oral contraceptives. This may result in reduced seizure control after the addition of an oral contraceptive, or adverse effects following withdrawal of an oral contraceptive. Dose adjustments of lamotrigine may be required.
In a study of 16 female volunteers, 30 mcg ethinylestradiol/150 mcg levonorgestrel in a combined oral contraceptive pill caused an approximately two-fold increase in lamotrigine oral clearance, resulting in an average 52% and 39% reduction in lamotrigine AUC and Cmax, respectively. Serum lamotrigine concentrations gradually increased during the course of the week of inactive medication (e.g. "pill-free" week), with pre-dose concentrations at the end of the week of inactive medication being, on average, approximately two-fold higher than during co-therapy.
The effect of other hormonal contraceptive products or hormone replacement therapy has not been evaluated although the effect may be similar.
Effect of lamotrigine on oral contraceptives:
Co-administration of 300mg lamotrigine in a study of 16 female volunteers had no effect on the pharmacokinetics of the ethinylestradiol component of a combined oral contraceptive pill. A modest increase in oral clearance of the levonorgestrel component was observed, resulting in an average 19% and 12% reduction in levonorgestrel AUC and Cmax, respectively. Measurement of serum follicle-stimulating hormone (FSH), luteinising hormone (LH) and estradiol during the study indicated some loss of suppression of ovarian hormonal activity, although measurement of serum progesterone indicated that there was no hormonal evidence of ovulation in any of the 16 subjects. The impact of the modest increase in levonorgestrel clearance, and the changes in serum FSH and LH, on ovarian ovulatory activity is unknown. Vaginal bleeding was reported by some volunteers (see section 4.4). The effects of doses of lamotrigine other than 300mg/day have not been studied and studies with other female hormonal preparations have not been conducted.'
Posted by woolav on August 15, 2005, at 7:42:36
In reply to Re: Lamictal and oral contraceptives » Kimbersaur, posted by ed_uk on August 15, 2005, at 4:55:23
I have a post on here too about the same thing. I take lamictal and trileptal, both which i have found out cause a decrease in the effectiveness of birth control. If I read Ed's response right, maybe increasing the dose will off set the problem. ??
I am going to discuss this with my pdoc this week.
what a bummer.
S
Posted by Kimbersaur on August 15, 2005, at 13:26:37
In reply to Re: Lamictal and oral contraceptives-kim, posted by woolav on August 15, 2005, at 7:42:36
Thanks, let me know what your pdoc says.
This is the end of the thread.
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