Subcutaneous versus Intramuscular Depot Methoxyprogesterone Acetate: A Comparative Review

Abstract

Depot medroxyprogesterone acetate (DMPA; Depo-Provera) is a highly effective and convenient contraceptive method that has been used worldwide for many decades. Recently, a new lower dose of DMPA, administered as a subcutaneous injection, has been approved for use in the USA as a contraceptive and a treatment for pain associated with endometriosis. The newer formulation has a similar efficacy to the older version and, more importantly, has fewer side effects, with improved user tolerability. Similar to the intramuscular DMPA injection (Depo-Provera intramuscular or contraceptive injection), the subcutaneous injection provides effective contraceptive and pain-management therapy for endometriosis, with a 3-monthly injectable protocol for women who seek long-term and reversible contraception without the need for a daily pill or a more frequent dosing regimen.

Keywords

contraception family planning subcutaneous injection subcutaneous medroxyprogesterone acetate women's health

Depo-Provera (150 mg/ml intramuscular [IM] depot medroxyprogesterone acetate [DMPA] – Depo-Provera IM or contraceptive injection) has been used around the world as a highly effective contraceptive for several decades [1]. It is a 3-monthly, progestin-only injectable contraceptive regimen that was approved in the USA in 1992 by the FDA.

As with any hormonal contraception, the goal is to use the lowest dose of hormones possible while providing the highest contraceptive efficacy. Consequently, the last 40 years have witnessed a consistent and considerable reduction in the hormonal dose of oral contraceptive pills. In this regard, DMPA-subcutaneous (SC) represents a lower-dose and different formulation of this highly effective and convenient progestin-only injectable contraceptive. It is important to emphasize the formulation variations in the SC and IM versions; therefore, the IM formulation cannot be dosed down and injected via the SC route.

Pharmacology & introduction to the compound

Medroxyprogesterone acetate (MPA) is a derivative of progesterone and is the active ingredient in DMPA-SC. Unlike the intramuscular injecton, DMPA-SC is administered by a subcutaneous injection. Jain and colleagues reported no pregnancies among women with over 16,000 cycles of exposure to DMPA-SC, indicating a comparable efficacy to DMPA-IM. While the active ingredient, MPA, is the same, DMPA-SC utilizes a different formulation of other ingredients compared with DMPA-IM. This unique formulation is pharmacologically different in so much as it provides 104 mg of DMPA/0.65 ml aliquot, translating to a 16% weight volume that optimizes SC delivery [2].

Chemistry

A slower rate of absorption is observed with the subcutaneous version, which allows for a lower peak serum MPA concentration and a longer duration of effect than is observed with DMPA-IM. Accordingly, with this 30% lower dose, serum MPA levels are maintained at an appropriate level to inhibit ovulation over the 3-month period between injections [3].

Pharmacodynamics & mechanism of action

As with other systemic progestin-only methods, both DMPA-IM and -SC prevent follicular maturation and thereby inhibit ovulation by suppressing luteinizing hormone and follicle-stimulating hormone surges. They also thicken cervical mucus and thus serve to create a barrier to sperm entering the upper reproductive tract. In addition, these progestin-only methods serve to slow tubal and endometrial mobility and cause the lining of the endometrium to become thinner [4,5]. These actions produce the contraceptive effects of DMPA-IM and -SC; contraceptive activity is thus achieved from disparate mechanisms and this likely increases the ability of DMPA to prevent pregnancy. The median time for return to ovulation among users of DMPA-SC was found to be 30 weeks, with a 97.4% cumulative rate of return to ovulation at 12 months [6]. This delayed return to fertility is also observed with the DMPA-IM injection and is the reason why consideration of DMPA-SC for pregnancy prevention is primarily geared towards women seeking longer-term contraception. Since the clinical trials on DMPA-SC were carried out primarily in Caucasian women, a single-center, single-dose, open-label trial conducted in Singapore with 24 Asian women was carried out to examine the effective suppression of ovulation in non-Caucasian women. This study found that among these Asian women, ovulation suppression was maintained for at least 91 days regardless of ethnicity and injection site [7].

Mild suppression of serum estradiol levels and a possible direct action on endometriotic implants are the likely pharmacological causes leading to the observed therapeutic effects of DMPA-SC on endometriosis-associated pain [8].

Pharmacokinetics & metabolism

Absorption

After a single SC administration of DMPA, serum concentrations of MPA reach 0.2 ng/ml or more within 24 h. The peak concentration is identified in serum approximately 1 week after injection. The mean trough concentrations at 6, 12 and 24 months were found to be 0.67, 0.79 and 0.87 ng/ml, respectively. Within the first 24 h after initial injection, contraceptive levels of MPA and decreased levels of serum progesterone and estradiol were demonstrated in Phase III trials [3].

Distribution

Plasma protein binding of MPA occurs with albumin and approximately 86% of MPA is plasma bound [8]. MPA is metabolized in the liver by the cytochrome P450 enzyme system. The terminal half-life of MPA is approximately 40 days after injection.

Special populations

No significant differences have been found in the pharmacokinetics or pharmacodynamics of MPA administration between African–American and Caucasian women [9]. Ovulation suppression was demonstrated in a Singaporean study that was designed to determine the basic pharmacokinetic profile of MPA and the duration of ovulation suppression after one injection of DMPA-SC in Asian women of various ethnic backgrounds [7]. Although total MPA exposure was lower in women who were obese in the trials, no dosage adjustment was required based on body weight [3]. Finally, no studies have evaluated the effect of hepatic and renal disease on the pharmacokinetics of this subcutaneous regimen.

Clinical efficacy

The perfect-use failure rate for DMPA-IM in the first year is 0.3%, whereas the typical-use failure rate in the first year is 3% [10], demonstrating the need for effective counseling prior to commencing this or any other contraceptive method. In the initial two open-label, multinational and multicenter contraceptive efficacy trials of the SC 104 mg regimen, no pregnancies were reported in 16,023 woman-cycles of exposure [3,6]. The women in these trials were from North and South America, Europe and Asia, and had a broad range of weights from 77–364 lbs. The continuation rate of DMPA-SC injections after 1 year was found to be 42–56%.

Safety & tolerability

DMPA-SC has a good safety and tolerability profile. The following are the advantages and disadvantages of this new formulation where noted; otherwise, information for DMPA-IM is reviewed when information for the newer formulation is not available.

Advantages

The overall advantages of DMPA, whether IM or SC, include decreases in blood loss, anemia and hemorrhagic corpus luteum cysts. It is a highly convenient method, as there is no need for daily dosing or a backup method of contraception if treatment is started within the first 5 days after the onset of menstrual flow. DMPA provides 13 weeks of continuous contraception and it is a private method as it requires no pill-packs, intravaginal strings, skin patches or SC devices. Advantages of the DMPA-SC formulation include its ability to be self-administered and the lower dosage of the active ingredient MPA. In a survey of 176 women visiting a family planning clinic in Edinburgh (UK), 67% expressed a preference to be able to self-administer their own DMPA-SC if possible [11]. In both Phase III trials, there was a very high level of satisfaction recorded among users of DMPA-SC, including preferring it to other contraceptive methods and a willingness to recommend this method to friends.

After 1 year of DMPA-SC use, 55% of women develop amenorrhea; 80% develop amenorrhea within 5 years of use, a similar rate to that observed with the DMPA-IM regimen. Thus, for women with bleeding diatheses or receiving anticoagulant medication, this is a method of birth control that can provide important noncontraceptive benefits. DMPA-IM has been shown to reduce sickle cell crises by approximately 70% [12]. DMPA-IM does not interfere with anticonvulsants and there are reports of decreased dysmenorrhea and ovulation pain. Further studies on these advantages of DMPA-IM need to be translated to the DMPA-SC formulation.

DMPA-SC is an effective, safe and convenient treatment for the pain associated with endometriosis and has been approved for this indication by the US FDA [13]. Compared with leuprolide acetate, DMPA-SC use results in considerably fewer side effects. In a recent multicenter trial in Italy, 300 women with laparascopically diagnosed endometriosis were assigned to 6 months of treatment with DMPA-SC or leuprolide acetate, with 12 months of post-treatment follow-up. Both treatments produced equivalent reductions in pain at 6 and 18 months. However, bone mineral density (BMD) reductions were significantly lower in the group treated with DMPA-SC as opposed to those treated with leuprolide [14]. In addition, in a trial lasting over 18 months, DMPA-SC and leuprolide acetate were found to have similar efficacy, but subjects receiving DMPA-SC experienced less bone loss and reported fewer and less severe menopausal symptoms [13,15]. In addition, DMPA-SC costs considerably less than leuprolide acetate. With all of these advantages, a higher compliance rate could be realized with the DMPA-SC regimen among women seeking endometriosis symptom relief.

More advantages of DMPA-IM use include a significant reduction in endometrial cancer, but there has been no documented reduction in ovarian cancer as yet, and such studies with the DMPA-SC formulation are not yet available [16].

Moreover, in DMPA-SC and -IM, suppression of ovulation was maintained with women with higher body mass indices (BMI) [17,18]. In the Phase III contraceptive trials, DMPA-SC was assessed in women with a broad range of weights (39–165 kg) and no pregnancies were observed [3]. Another advantage found in these trials is for women who are hypertensive, as DMPA-IM and -SC do not increase blood pressure and do not impact the risk for adverse cardiovascular events. No significant changes in blood pressure were observed in users over the course of the study periods in these two trials. A final advantage is that both DMPA-SC and -IM are appropriate for women who are breastfeeding, as they contain no estrogen.

Future advantages of this SC formulation include the potential for at-home self-administration. Moreover, use of the DMPA-SC formulation may lend itself to providing suppression of pituitary function and ovarian estradiol production for women with diseases and conditions affected by these endocrine processes.

Disadvantages

The disadvantages of DMPA-SC include irregular menses during the first several months. Over the course of a 1-year exposure to DMPA-SC, irregular bleeding episodes decreased, while amenorrhea increased [3]. By 12 months in these trials, it was noted in the Phase III studies that 55% of women using DMPA-SC developed amenorrhea. The frequency of amenorrhea is similar to that observed among users of DMPA-IM in whom, after 6–12 months of use, amenorrhea becomes the most common bleeding profile [19].

Many users experience unpredictable spotting and bleeding. During the first month following the initial injection of DMPA-SC, most women experienced some degree of bleeding or spotting [3]. In a study comparing 1-year levonorgestrel-releasing implants, DMPA and oral norethindrone, only the DMPA group showed a progressive increase in amenorrhea. At the completion of the 12-month study, the DMPA group had significantly fewer total days of blood loss than those using levonorgestrel implants or norethindrone [20]. Nonetheless, breakthrough spotting and bleeding may interfere with sexual activity and other lifestyle considerations.

The occurrence of unscheduled bleeding associated with progestin-only contraceptives is not completely understood. Varying stages of endometrial disruption and some atrophy caused by MPA may result from suppression of circulating estradiol levels.

The most common side effects encountered with DMPA-SC in the Phase III trials included headache (11.8–5.0%), weight gain (8.5%), intermenstrual bleeding (7.9–6.4%), amenorrhea (8.1–5.8%) and decreased libido (5.1%) [3]. There was a median weight change of 1.4–1.7 kg in these trials.

DMPA-SC and -IM are long-acting methods and are not immediately reversible, with a slow return to baseline fertility; an average of 10 months from the last injection to pregnancy was observed in the Phase III trials mentioned previously. The relatively hypoestrogenic state observed in some women using DMPA-SC and -IM formulations may cause some dyspareunia, occasional hot flashes or decreased libido. Acne and hirsuitism may also result from these two DMPA formulations. Some concerns regarding an increase in depression, anxiety and other mood changes among users has been mentioned by some investigators, although most studies show no overall adverse effect on mood [21]. Severe depression is rare and appears to occur no more frequently than in the general population.

The metabolic effects of DMPA-IM may include a slight rise in glucose and low-density lipoprotein, and a decrease in high-density lipoprotein. Other side effects of DMPA-IM commonly include breast tenderness, bloating, transient hair loss and vasomotor symptoms. However, no such adverse effects were demonstrated in the studies evaluating DMPA-SC.

There is the potential for a decline in BMD during the first 2–4 years of DMPA-IM use, after which BMD usually stabilizes at approximately 5% below baseline levels. The magnitude of effect seen in cross-sectional studies of long-term users shows an approximate reduction of 0.5 standard deviations at hip and spine compared with nonusers, an effect similar to that observed among women who breastfeed. In longitudinal studies of adults and adolescents, around 5–7% of bone is lost (approximately 0.5 standard deviations at hip and spine after 2 years of use). The rate of loss appears to decrease over time. If DMPA-IM is discontinued prior to the menopause, the resulting increase in estrogen levels will lead to substantial recovery of BMD towards baseline. On discontinuation of DMPA-IM, BMD increases regardless of age, except in those who have reached menopause; and within a 2- to 3-year period, BMD recovers to the level of a comparable DMPA-IM nonuser population.

One study has shown that BMD in post-menopausal women does not differ based on prior DMPA-IM use versus nonuse [22]. In a study by Cundy, women who used DMPA-IM for 5 years or more had significantly reduced BMD of the lumbar spine and femoral neck (especially after 15 years of use and if started before the age of 20 years) [23]. A meta-analysis of 12 studies including 1039 DMPA-IM users and 2086 controls found that the number of standard deviations below average bone density (T-score) averages in the DMPA-IM users decreased by less than one standard deviation, compared with nonusers [24]. These reductions stabilized after 3–4 years of use and radiographic evidence of BMD loss was reversed when the drug was discontinued [25,26]. A recent report from Scholes and colleagues followed 170 adolescents and found that BMD was substantially complete 12 months following discontinuation of DMPA-IM [27]. The duration of use of DMPA-IM in this study did not impact the speed of BMD recovery following discontinuation. Despite the overwhelming evidence that DMPA-IM use has an adverse effect on BMD measurements, no study has ever demonstrated an increased risk of fracture or other bone-related adverse outcomes among users in their pre-, peri- or postmenopausal years.

In July 2005, the WHO issued a statement concluding that DMPA-IM reduces BMD in women who have attained peak bone mass, and impairs the acquisition of BMD in those who have not yet attained peak bone mass (adolescents and young women). The statement confirmed that there are not enough data to indicate whether women who had yet to reach peak bone mass would be affected – in other words, whether the recovery seen in women who had attained peak bone mass could in fact apply to those who were still growing. In addition, women using DMPA-IM during the menopausal transition, who would be losing bone due to their age, could also be at risk in that they would not have had a period of recovery before they enter menopause. Furthermore, there is not enough evidence to assess whether DMPA-IM use modified the fracture risk of women using this formulation in the long term. However, since the effect of DMPA-IM on fracture risk is reversible, any lifetime increase in fracture risk is likely to be small [28]. Finally, since all of these data come from studies on women using DMPA-IM, more studies are needed on the effects of the DMPA-SC formulation on BMD; however, for now, these recommendations also apply to DMPA-SC.

Regulatory affairs

The US FDA recently added a black box warning to the package insert cautioning against the long-term use of DMPA. It raises concerns regarding reduced BMD that may increase with duration of use and may not be entirely reversible [8]. The US FDA recommends that DMPA-SC or -IM be utilized as long-term birth control (meaning for more than 2 years) only if other methods are inadequate. This recommendation should be placed into the perspective of an individual woman's need for a safe and effective contraceptive method, given her other risk factors for osteoporosis including alcohol intake, tobacco use, eating disorders or corticosteroid use, as well as the lack of BMD-monitoring protocols for premenopausal women [29] and the lack of evidence that DMPA-SC or -IM increase the risk of fracture at any time of a woman's life. For many women, DMPA-SC may be the contraceptive method most suitable to her contraceptive needs and lifestyle, so that discontinuation after 2 years of use could place her at an increased risk for unintended pregnancy. Despite this theoretical concern of an adverse effect on BMD, these measurements are not recommended for DMPA-SC users as they do not predict fracture risk in nonmenopausal women. Obtaining such measurements is inappropriate, as is monitoring BMD in a lactating woman, another condition that has been shown to lead to reversible BMD reductions with no adverse effect on risk of fracture.

Executive summary

Mechanism of action

As with other systemic, progestin-only methods, depot medroxyprogesterone acetate (DMPA) prevents follicular maturation and thereby inhibits ovulation by suppressing luteinizing hormone and follicle-stimulating hormone surges.

DMPA thickens the cervical mucus, which blocks sperm from entering the upper reproductive tract and causes slower tubal and endometrial mobility.

DMPA also causes the lining of the endometrium to become thinner.

Pharmacokinetic properties

DMPA-subcutaneous (SC) is a new formulation of this drug.

The peak serum concentration is approximately 1 week after injection.

Medroxyprogesterone acetate (MPA) is metabolized in the liver by the cytochrome P450 enzyme system.

No significant differences in the pharmacokinetics or pharmacodynamics of MPA administration have been demonstrated among different races or ethnicities.

Although total MPA exposure was lower in women who were obese in the trials, no dosage adjustment was required based on body weight.

No studies have evaluated the effect of hepatic and renal disease on the pharmacokinetics of DMPA-SC.

Clinical efficacy

The perfect-use failure rate in first year is 0.3%, whereas the typical-use failure rate in the first year is 3%.

In the initial two open-label, multinational and multicenter Phase III studies of the SC 104 mg regimen, no pregnancies were reported in 16,023 woman-cycles of exposure.

Safety & tolerability

DMPA decreases blood loss, anemia and hemorrhagic corpus luteum cysts.

In both Phase III trials, there was a very high level of satisfaction among users.

After 1 year of use, 55% of women develop amenorrhea; 80% develop amenorrhea within 5 years.

For women with bleeding diatheses or receiving anticoagulant medication, DMPA can provide important noncontraceptive benefits.

It has been shown to reduce sickle cell crises by approximately 70%.

DMPA does not interfere with anticonvulsants.

DMPA-SC is an effective, safe and convenient treatment for the pain associated with endometriosis.

Compared with leuprolide acetate, DMPA-SC has fewer side effects.

Suppression of ovulation was maintained in women with a higher body mass index.

It also is appropriate for women who are breastfeeding.

In neither of the Phase III trials was there a significant change in blood pressure in users over the study periods - this represents an advantage for women who are hypertensive.

DMPA is long acting and not immediately reversible, with a slow return to baseline fertility: an average of 10 months from the last injection.

The relative hypoestrogenic state in some women using DMPA may cause some dyspareunia, occasional hot flashes, decreased libido, acne and hirsuitism.

Most studies show no overall adverse effect on mood. Severe depression is rare.

There is a potential for decline in bone mineral density (BMD) during the first 2–4years of use, after which BMD usually stabilizes approximately 5% below baseline levels, representing a change of approximately 0.5 standard deviations below average.

If DMPA is discontinued prior to the menopause, the resulting increase in estrogen levels will lead to substantial recovery of BMD towards baseline. One study has shown that BMD in postmenopausal women does not differ based on prior DMPA use versus nonuse.

Drug interactions

No drug-drug interactions studies have been conducted with DMPA-SC.

Aminoglutethimide administered concomitantly with DMPA-SC may significantly decrease the serum concentrations of MPA.

Dosage & administration

DMPA-SC must be given by injection into the anterior thigh or abdomen once every 3 months (12-14 weeks).

The dosage does not need to be adjusted for body weight.

The prefilled syringe must be shaken just before use to create a uniform suspension.

Clinicians should ensure that the patient is not pregnant at the time of first injection or injection after 14 weeks.

Candidates for use

Candidates include women who desire long-term contraception and can return for an office visit every 11–13 weeks. This is a good option for women who wish to have privacy and convenience with contraception. In addition, this contraceptive method is a good choice for those who cannot or should not use estrogen (e.g., history of deep vein thrombosis, smokers over the age of 35 years, women who use medications that affect the clearance of the liver, and women with sickle-cell disease, fibroids, anemia, seizure disorder, systemic lupus erythematosus or endometriosis) [30]. This method should also be considered for women with disabilities for whom vaginal bleeding is a hygiene and maintenance-of-care issue.

Conclusion

DMPA-SC offers women a new and highly effective option for contraception. While providing a 31% lower total dose of MPA than the IM formulation, the lower dose formulation effectively suppresses ovulation for at least 13 weeks in all subjects regardless of ethnicity/race or BMI. However, the side effect of irregular bleeding is quite common, as with the IM injection, and two studies have demonstrated that women are more likely to continue to use DMPA-SC if counseled about the bleeding side effects when they start using this method of contraception [31,32]. The convenience of DMPA-SC and its relatively long action lend itself to greater satisfaction among potential users. Since being introduced in the USA in 1992, DMPA-IM use has been considered, to a major extent, to be responsible for the declining rates of unintended pregnancies and abortions in the USA, especially among teenagers [33]. It is hoped that this newer formulation of DMPA, specifically designed for SC administration, may further facilitate this downward trend in unintended pregnancies in the USA and around the world.

Future perspective

Over the next 5–10 years, contraceptive technology will continue to advance. Nevertheless, despite the fact that there are numerous methods, there are still millions of women worldwide who are using no form of contraception. DMPA-SC could help fill this gap, especially through self-administration at home.

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