Long-acting reversible contraception (LARC) is defined as any method of contraception that does not have to be used or applied more than once a cycle or once a month.
This includes the following methods:
- Non-hormonal - copper intrauterine devices (IUD)
- Progestogen-only methods:
- intrauterine systems (IUS)
- progestogen-only injectable contraceptives
- progestogen-only subdermal implants
The progestogen-only long-acting delivery systems release low constant doses of progestogen. Delivery of the highest dose is injectable. These methods also avoid first-pass metabolism through the liver because they are not orally administered.
Each method should be evaluated on the basis of:
- contraceptive efficacy
- duration of action following application or use
- risks and adverse effects
- benefits of use unrelated to contraception
- how it is initiated or stopped
- warning signs to seek medical help during use
Benefits of Long-Acting Reversible Contraception
All LARC are more cost-effective than the oral contraceptive pill.
Among the LARC methods, the most cost-effective are the IUDs, the IUS, the injectables, and the implants
Mode of action
Each method works differently depending on the delivered dose of hormone.
Injectables, which deliver higher doses, act primarily by inhibiting the ovarian cycle to suppress ovulation.
Lower doses, as is delivered via implants, do not completely suppress follicle development, but inhibit ovulation nonetheless.
The lowest doses are delivered by the IUS and the older Norplant implant. These act primarily by rendering the cervical mucus hostile to penetration, and causing endometrial thinning. This latter effect is particularly prominent with the IUS which results in an atrophic endometrium.
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The progestogen-only long-acting methods are suitable for women who cannot tolerate or have contraindications to the use of estrogen. This means that they can be used by women who:
- smoke, even if they use over 15 cigarettes a day or are more than 35 years old
- have current or past ischemic heart disease
- have had a cerebrovascular accident (stroke)
- have liver disease, whether infective, tumorous, or cirrhotic
- are facing immobilization due to major surgery
- history of or current deep venous thrombosis
- Hypertension which is poorly or only moderately controlled
- Current or history of breast cancer within the last five years
- Are in the immediate postpartum, namely, within three weeks of birth if not lactating, and the first four weeks if lactating
- are obese or overweight
- have diabetes
- have a history of migraine with or without aura
- are on liver-enzyme inducing drugs, which speed up the hepatic metabolism of estrogen, such as phenytoin or barbiturates
DMPA may reduce seizure frequency in epileptics
Menstrual differences almost always occur with the use of the progestogen-only methods. If regular ovulation continues, bleeding occurs in line with regular menstruation. If ovulation is completely suppressed, the woman will experience amenorrhea, which is characteristic of the injectable DMPA and the IUS. With some follicular development still present, endometrial growth occurs but in an unpredictable fashion, causing irregular bleeding, as is seen with the implants.
When follicular development is disrupted, this may result in abnormally large follicles and the subsequent formation of follicular ovarian cysts, seen in up to a fifth of women on the IUS. These women are typically asymptomatic.
Metabolic side effects
Women on progestogen-only methods may suffer from acne, headaches, fluid retention, mood fluctuations, and weight gain. The last mentioned is significantly greater with DMPA.
The pregnancy rate is extremely low with these methods. However, when pregnancy occurs there is a high risk of ectopic gestation due to slowed tubal motility in response to progestogen. The overall risk is considered to be the same as for women not on any contraceptives.
This has been poorly studied, but there is some evidence for a slight decline in endometrial cancer among users of progestogen-only contraception.
Cardiovascular disease including venous thromboembolism
These methods are not associated with a higher risk of these conditions if the user population is properly defined (since it often contains women at an increased risk of VTE).
Gall bladder disease
This may be slightly increased with the use of older norethisterone implants, but not with other methods.
Bone mineral density
Injectables such as DMPA may cause hypoestrogenism, which is responsible for bone mineral density loss and a possibly higher risk of osteoporosis.
Sexually transmitted diseases
Women who are at increased risk of STIs may develop pelvic inflammatory disease following the use of IUDs or IUS.
Return to fertility
Fertility is resumed quite promptly with most progestogen-only methods except with the injectables, which is associated with a temporary but significant delay. Mean pregnancy rates improve with time to match those of other methods, however.
The Intra-Uterine System
The IUS is a slender T-shaped plastic device that contains progestogen. This hormone is normally secreted as part of the ovarian cycle. It is released from the IUS in a sustained and slow manner, acting as a contraceptive for three to seven years depending on the model used. This constant low concentration of progesterone in the body causes several effects resulting in contraception, such as thinning of the endometrium to prevent implantation, inhibiting ovulation, and rendering the cervical mucus unreceptive to sperm, thereby preventing fertilization. Endometrial atrophy is extremely common, causing amenorrhea to develop within six to twelve months.
It is more than 99 percent effective. Fertility returns promptly upon removal of the device.
60 percent of women on the IUS who discontinue it within a year do so because of excessive or irregular bleeding and dysmenorrhea.
Although it is rare - affecting less than one in one thousand - uterine perforation may occur. The risk of PID is least with this method.
Progestogen‑Only Injectable Contraceptives
These act primarily on the ovarian cycle and prevent ovulation. The depot form of progesterone used releases the drug at a very low rate for three months. It has to be repeated regularly, at 12 week intervals for depot medroxy progesterone acetate (DMPA), and 8-weekly with norethisterone enanthate (NET-EN). 150 mg of DMPA is given by deep intramuscular injection into the lateral aspect of the thigh or the gluteal muscles.
The pregnancy rate is less than 0.4 percent. The return of fertility may be delayed after stopping the use of injectable contraception.
Half of all DMPA users stop the injection within a year, chiefly due to menstrual irregularities, especially amenorrhea. Significant weight gain and loss of bone mineral density are commonly reported. Fortunately, it lowers the risk of endometrial and ovarian cancer.
Progestogen‑Only Subdermal Implants
These are 40 mm long plastic rods containing 68 mg of etonogestrel, released slowly over at least three years. It is inserted subdermally in the upper arm. It has a very low failure rate of less than 1 percent.
Irregular bleeding patterns, with amenorrhea, polymenorrhea, oligomenorrhea, or prolonged bleeding, may occur. It does reduce dysmenorrhea, and fertility returns promptly after discontinuation.
These are thin T-shaped devices with a copper core or copper banded round the arms, the total copper content being 380 sq. mm. They last for up to 10 years and have a high efficacy of 98-99 percent. They are reported to be most useful in women who wish to postpone their next child for at least two years. They act primarily by inhibiting implantation, the copper ions rendering the endometrium hostile to the zygote and destroying sperms within the uterine cavity. It thus prevents fertilization and inhibits implantation.
Symptoms such as menorrhagia and dysmenorrhea are increased. One in twenty pregnancies with a Cu-T in situ is ectopic, though the overall risk is lower. The odds of developing pelvic inflammatory disease risk are higher in women who are prone to sexually transmitted infections (STIs), but who use copper-T.
During its use, the woman is not exposed to hormones, and upon its removal, her fertility is promptly restored. It is also sometimes used as emergency contraception.
Both IUDs and IUS are suitable for nulliparas, and may be inserted at any time of the month with a small risk of infection for a few days following. There is also a small risk of uterine perforation.
Expulsion is most likely when inserted for nulliparous women, and during the first year of use, as well as in women who have the device inserted in the immediate postpartum or post-abortion period.