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Injection (medicine)
Combined injectable birth control
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Combined injectable birth control

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Combined injectable birth control
Background
Type Hormonal
First use By 1969
Failure rates (first year)
Perfect use 0–0.2%
Typical use ?
Usage
Duration effect 1 month
User reminders ?
Advantages and disadvantages
STI protection No
Benefits Especially good if poor pill compliance

Combined injectable contraceptives (CICs) are a form of hormonal birth control for women. They consist of monthly injections of combined formulations containing an estrogen and a progestin to prevent pregnancy.

CICs are different from progestogen-only injectable contraceptives (POICs), such as depot medroxyprogesterone acetate (DMPA; brand names Depo-Provera, Depo-SubQ Provera 104) and norethisterone enantate (NETE; brand name Noristerat), which are not combined with an estrogen and are given once every two to three months instead of once a month.

Hormonal contraception works primarily by preventing ovulation, but it may also thicken the cervical mucus inhibiting sperm penetration. Hormonal contraceptives also have effects on the endometrium, that theoretically could affect implantation.

Medical uses

CICs are administered by intramuscular injection into the deltoid, gluteus maximus, or anterior thigh. They are ideally administered every 28 to 30 days, though they have been demonstrated to be effective up to 33 days.

Some CICs have been said to be used by transgender women as a means of feminizing hormone therapy as well.

Available forms

Combined injectable contraceptives marketed for clinical use
Composition Dose Vehicle Brand Names Availability
Estradiol valerate / Norethisterone enantate 5 mg /
50 mg		 Oil solution Multiple Approved in at least 36 countries
Estradiol cypionate / Medroxyprogesterone acetate 5 mg /
25 mg		 Microcrystalline aqueous suspension Multiple Approved in at least 18 countries
Estradiol enantate / Algestone acetophenidea 10 mg /
150 mg		 Oil solution Multiple Approved in at least 19 countries
5 mg /
75 mg		 Oil solution Anafertin†, Patector NF, Yectames Approved at least 9 countries
10 mg /
120 mg		 Oil solution Unalmes, Yectuna Approved in at least 3 countries
10 mg /
75 mg		 Oil solution Ova Repos† Discontinued (firm was in Spain)
Estradiol benzoate butyrate / Algestone acetophenide 10 mg /
150 mg		 Oil solution? Redimen, Soluna, Unijab, Unimens§ Approved in Peru and Singapore
Estradiol valerate / Hydroxyprogesterone caproate 5 mg /
250 mg		 Oil solution Chinese Injectable No. 1 Approved in China
Estradiol / Megestrol acetate 3.5 mg /
25 mg		 Microcrystalline aqueous suspension Chinese Injectable No. 2, Mego-E Approved in China
Estradiol cypionate / Hydroxyprogesterone caproate 5 mg /
250 mg		 Oil solution? Sinbios† Discontinued (firm was in Mexico)
Estradiol valerate / Estradiol benzoate / Hydroxyprogesterone caproate 10 mg /
1 mg /
250 mg		 Oil solution? Sin-Ol† Discontinued (firm was in Mexico)
Notes: All are given by intramuscular injection once a month. Footnotes: † = Discontinued. § = Never marketed. a = Unsorted brand names (doses unknown; for E2-EN/DHPA): Evitas† and Femineo†. Sources:

A variety of different CICs, generally containing a short-acting natural estradiol ester and a long-acting progestin ester, are available for clinical use. Estrogens that are used include estradiol valerate, estradiol cypionate, estradiol enantate, estradiol benzoate butyrate, and estradiol, while progestins that are used include norethisterone enantate, medroxyprogesterone acetate, algestone acetophenide (dihydroxyprogesterone acetophenide), hydroxyprogesterone caproate, and megestrol acetate.Estradiol benzoate has a duration that is too short for once-monthly CICs, and is not used in them. Conversely, estradiol enantate is said to have a duration that is too long for once-monthly CICs, but is nonetheless used in them.

Side effects

Side effects of CICs, besides menstrual bleeding changes, are minimal. The most prominent side effects of CICs are menstrual irregularities during the first 3 to 6 months of use.Dysmenorrhea has been reported in 30 to 65% of women. Other side effects include breast tenderness/pain, headache, and libido changes. Some fluid retention can occur, but weight gain is minimal. Local injection site reactions have also been reported in 15 to 35% of women.

Effects of CICs on coagulation and fibrinolysis are minimal and are not thought to be clinically relevant. Conversely, combined oral contraceptive pills containing ethinylestradiol have considerable effects on coagulation and fibrinolysis. The differences can be attributed to the lack of the first-pass effect with parenteral administration as well as structural and pharmacological differences between estradiol and ethinylestradiol.

Pharmacology

Idealized curves of estradiol levels over a period of 30 days after injection of different estradiol esters in women.

CICs contain an estrogen and a progestin. The estrogen is generally a short-acting estradiol ester, which acts as a prodrug of estradiol. Esters of estradiol are natural and bioidentical estrogens, and are believed to have more favorable effects on lipid metabolism, cardiovascular health, and hemostasis than synthetic estrogens such as ethinylestradiol. The progestin is a long-acting progestogen ester, which may or may not act as a prodrug.Progesterone derivatives including medroxyprogesterone acetate, algestone acetophenide (dihydroxyprogesterone acetophenide), hydroxyprogesterone caproate, and megestrol acetate are active themselves and are not prodrugs, whereas the testosterone derivative norethisterone enantate is a prodrug of norethisterone. Regardless of whether they are prodrugs or not, steroid esters form a depot and have an extended duration of action due to a depot effect when administered by intramuscular or subcutaneous injection.

Because CICs are administered parenterally, they bypass the first-pass effect in the liver and intestines that occurs with oral administration of estrogens. However, is estimated that about 20% of an administered dose does still eventually pass through the liver. Hence, these preparations are not completely liver-neutral. Nonetheless, they have dramatically reduced hepatic effects relative to oral ethinylestradiol. In addition, parenteral estradiol in general has about 4- or 5-fold reduced potency in the liver than oral estradiol.

Hormone levels following a single intramuscular injection of estradiol valerate/norethisterone enanthate (5 mg/50 mg) (Mesigyna) in healthy young men. Testosterone levels were maximally suppressed by about 94%, to ~30 ng/dL, when measured at day 7 post-injection.

CICs have antigonadotropic effects via their estrogenic and progestogenic activity and inhibit fertility and suppress sex hormone levels. A single intramuscular injection of estradiol valerate/norethisterone enanthate (5 mg/50 mg) (Mesigyna) has been found to strongly suppress testosterone levels in men. Testosterone levels decreased from a baseline of ~503 ng/dL to a trough of ~30 ng/dL (a 94% decrease) which occurred at day 7 post-injection.

Estradiol levels with combined injectable contraceptives
Preparation Form Dose Estradiol Cmax Estradiol Tmax
EV/NETE Oil solution 5 mg/50 mg 232–428 pg/mL 2 days
EC/MPA Aqueous suspension 5 mg/25 mg 184–736 pg/mL 2–4 days
EEn/DHPA Oil solution 10 mg/150 mg 314–317 pg/mL 4.2–8.1 days
5 mg/75 mg 148 pg/mL 6.5 days
Potencies and durations of natural estrogens by intramuscular injection
Estrogen Form Dose (mg) Duration by dose (mg)
EPD CICD
Estradiol Aq. soln. ? – <1 d
Oil soln. 40–60 – 1–2 ≈ 1–2 d
Aq. susp. ? 3.5 0.5–2 ≈ 2–7 d; 3.5 ≈ >5 d
Microsph. ? – 1 ≈ 30 d
Estradiol benzoate Oil soln. 25–35 – 1.66 ≈ 2–3 d; 5 ≈ 3–6 d
Aq. susp. 20 – 10 ≈ 16–21 d
Emulsion ? – 10 ≈ 14–21 d
Estradiol dipropionate Oil soln. 25–30 – 5 ≈ 5–8 d
Estradiol valerate Oil soln. 20–30 5 5 ≈ 7–8 d; 10 ≈ 10–14 d;
40 ≈ 14–21 d; 100 ≈ 21–28 d
Estradiol benz. butyrate Oil soln. ? 10 10 ≈ 21 d
Estradiol cypionate Oil soln. 20–30 – 5 ≈ 11–14 d
Aq. susp. ? 5 5 ≈ 14–24 d
Estradiol enanthate Oil soln. ? 5–10 10 ≈ 20–30 d
Estradiol dienanthate Oil soln. ? – 7.5 ≈ >40 d
Estradiol undecylate Oil soln. ? – 10–20 ≈ 40–60 d;
25–50 ≈ 60–120 d
Polyestradiol phosphate Aq. soln. 40–60 – 40 ≈ 30 d; 80 ≈ 60 d;
160 ≈ 120 d
Estrone Oil soln. ? – 1–2 ≈ 2–3 d
Aq. susp. ? – 0.1–2 ≈ 2–7 d
Estriol Oil soln. ? – 1–2 ≈ 1–4 d
Polyestriol phosphate Aq. soln. ? – 50 ≈ 30 d; 80 ≈ 60 d
Notes and sources
Notes: All aqueous suspensions are of microcrystalline particle size. Estradiol production during the menstrual cycle is 30–640 µg/d (6.4–8.6 mg total per month or cycle). The vaginal epithelium maturation dosage of estradiol benzoate or estradiol valerate has been reported as 5 to 7 mg/week. An effective ovulation-inhibiting dose of estradiol undecylate is 20–30 mg/month. Sources: See template.
Parenteral potencies and durations of progestogens
Compound Form Dose for specific uses (mg) DOA
TFD POICD CICD
Algestone acetophenide Oil soln. - – 75–150 14–32 d
Gestonorone caproate Oil soln. 25–50 – – 8–13 d
Hydroxyprogest. acetate Aq. susp. 350 – – 9–16 d
Hydroxyprogest. caproate Oil soln. 250–500 – 250–500 5–21 d
Medroxyprog. acetate Aq. susp. 50–100 150 25 14–50+ d
Megestrol acetate Aq. susp. - – 25 >14 d
Norethisterone enanthate Oil soln. 100–200 200 50 11–52 d
Progesterone Oil soln. 200 – – 2–6 d
Aq. soln. ? – – 1–2 d
Aq. susp. 50–200 – – 7–14 d
Notes and sources:

History

The first CIC to be studied was estradiol valerate/hydroxyprogesterone caproate (EV/OHPC) in 1963, and the second CIC to be studied was estradiol enantate/algestone acetophenide (E2-EN/DHPA) in 1964. In 1967, E2-EN/DHPA was in the late stages of clinical development. By 1969, the medication was available for medical use under the brand name Perlutal. Within a few years, it was marketed under other brand names such as Topasel and Ova-Repos as well. In addition, several other CICs had been introduced for medical use by 1972. By 1976, two major CICs were in use: E2-EN/DHPA (brand names Perlutan, Topasel) in Spain and Latin America, and EV/OHPC (brand name Injectable No. 1) in China. These CICs have been described as first-generation CICs. Two second-generation CICs, estradiol cypionate/medroxyprogesterone acetate (EC/MPA; brand names Cyclofem and later Lunelle) and estradiol valerate/norethisterone enantate (EV/NETE; brand name Mesigyna), were introduced for clinical use in 1993. On 5 October 2000, Pharmacia received FDA approval for Lunelle Monthly Contraceptive Injection. In April 2003, Pharmacia was acquired by Pfizer (makers of depot medroxyprogesterone acetate). In October 2003, Lunelle was discontinued in the United States.

Society and culture

Availability

Known availability of CICs in countries throughout the world (as of September 2018).

CICs are available in many countries throughout the world, including widely throughout Central and South America, in Mexico and the Caribbean, in China, in several Southeast Asian and African countries, and in Turkey. They were also previously available in the United States, Portugal, and Spain, but have been discontinued in these countries.

Research

Many other CICs have been studied but have not been approved or marketed for clinical use.

The following are marketed CICs at different doses than those that are approved:

The half-progestin-dose formulation of estradiol valerate/norethisterone enantate (5 mg / 25 mg) is also known as HRP-103 and the half-progestin-dose formulation of estradiol cypionate/medroxyprogesterone acetate (5 mg / 12.5 mg) is also known as HRP-113.

The following are CICs that have never been marketed:

See also

Further reading


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