A balancing act

I. Milsom

The drive to reduce estrogen-related side effects has led to a progressive reduction in the estrogen dose of combined hormonal contraceptives. However, lower estrogen-dosed combined oral contraceptives (COCs) have been associated with unacceptable changes in bleeding pattern, the main factor affecting user compliance and satisfaction. A recent Cochrane review found that women taking lower estrogen-dosed COCs were more likely to discontinue studies earlier and have more disruptions to bleeding patterns than women using COCs with higher estrogen doses.

The pharmacokinetics of the vaginal route of hormonal delivery has enabled NuvaRing® (15 µg ethinylestradiol (EE)/120 µg etonogestrel daily) to defy this paradigm. The unique route of administration delivers consistent and steady serum hormonal levels that contribute to NuvaRing's excellent cycle control profile. In a recent large-scale, randomized, comparative clinical trial to compare NuvaRing's cycle control and tolerability with a COC containing 30 µg EE/3 mg drospirenone (Yasmin), breakthrough bleeding or spotting during cycles 2-13 was generally less frequent with NuvaRing (3.6-6.2%) than with the COC (4.7-10.4%) and showed a statistically significant odds ratio of 0.61 (95% CI: 0.46, 0.80) with longitudinal analysis. Intended bleeding (a representation of an ideal bleeding pattern) was significantly better for all cycles with NuvaRing than the COC (p<0.01). These results confirm the findings of a previous similarly designed trial in which NuvaRing was compared with a COC containing levonorgestrel (LNG) and 30 µg EE.

NuvaRing's superior bleeding profile is particularly attractive to women wishing to change from their current hormonal contraceptive. A recent pooled data analysis showed that women are less likely to experience irregular bleeding when switching to NuvaRing compared with COCs (30 µg EE/150 µg LNG and 30 µg EE/3 mg drospirenone).

The other side of this balancing act-achieving a low incidence of estrogen-related side effects-is accomplished through NuvaRing's low estrogen exposure. In the comparative trial between NuvaRing and Yasmin, women in the NuvaRing group consistently reported a lower incidence of nausea, headache and breast pain than those in the Yasmin group. Body weight, another factor affecting compliance and tolerability, was also assessed in this study. Changes from baseline in mean bodyweight and body composition parameters were relatively small for both groups with no notable between-group differences.

It is well established that NuvaRing, with the convenience of monthly dosing, is as effective as the Pill. Furthermore, its unique pharmacokinetic properties enables NuvaRing to successfully achieve the previously unattainable balancing act of excellent cycle control and low estrogen-related side effects. Thus, the conventional paradigm of having to choose between cycle control and estrogen-related side effects does not apply.