had unprotected intercourse 96 – 120 hours ago (even if she
has also had unprotected intercourse within the last
96 hours). It should also be consideredfirst line for a woman
who has had unprotected sexual intercourse within the last
5 days if it is likely to have taken place during the 5 days
before the estimated day of ovulation.h
Hormonal emergency contraception interactions
See Contraceptives, interactions below.
Starting hormonal contraception after emergency hormonal
contraception
Emergency hormonal contraception methods donotprovide
ongoing contraception.gAfter taking levonorgestrel,
women should start suitable hormonal contraception
immediately. They must use condoms reliably or abstain
from intercourse until contraception becomes effective.
Women should wait 5 days after taking ulipristal acetate
before starting suitable hormonal contraception. Women
must use condoms reliably or abstain from intercourse
during the 5 day waiting period and also until their
contraceptive method is effective.h
The copper intra-uterine device immediately provides
effective ongoing contraception.
Useful Resources
Emergency Contraception. The Faculty of Sexual and
Reproductive Healthcare. Clinical guidance. March 2017.
http://www.fsrh.org/standards-and-guidance/documents/ceu-clinical-
guidance-emergency-contraception-march- 2017
Contraceptives, interactions 06-Jun-2017
Overview
The effectiveness ofcombinedoral contraceptives,
progestogen-onlyoral contraceptives, contraceptive patches,
vaginal rings, and emergency hormonal contraception can be
considerably reduced by interaction with drugs that induce
hepatic enzyme activity (e.g. carbamazepine p. 196 ,
eslicarbazepine acetate, nevirapine p. 414 , oxcarbazepine
p. 204 , phenytoin p. 205 , phenobarbital p. 216 , primidone
p. 217 , ritonavir p. 426 , St John’s Wort, topiramate p. 212
and, above all, rifabutin p. 364 and rifampicin p. 364 ) and
possibly also griseofulvin p. 379 .gA condom together
with a long-acting method (such as an injectable
contraceptive) may be more suitable for patients with HIV
infection or at risk of HIV infection; advice on the possibility
of interaction with antiretroviral drugs should be sought
from HIV specialists.h
Combined hormonal contraceptives interactions
gWomen using combined hormonal contraceptive
patches, vaginal rings or oral tablets who require enzyme-
inducing drugs or griseofulvin should be advised to change
to a reliable contraceptive method that is unaffected by
enzyme-inducers, such as some parenteral progestogen-only
contraceptives (medroxyprogesterone acetate p. 512 and
norethisterone p. 479 ) or intra-uterine devices
(levonorgestrel p. 508 ; see also Contraceptives, non-
hormonal p. 496 ). This should be continued for the duration
of treatment and for four weeks after stopping. If a change in
contraceptive method is undesirable or inappropriate the
following options should be discussed:h
Short course (2 months or less) of an enzyme-inducing drug
gContinuing the combined hormonal contraceptive
method may be appropriate if used in combination with
consistent and careful use of condoms for the duration of
treatment and for four weeks after stopping the enzyme-
inducing drug.h
Long-term course (over 2 months) of an enzyme-inducing drug
(except rifampicin or rifabutin) or a course of griseofulvin
gUse a monophasic combined oral contraceptive at a
dose of ethinylestradiol^50 micrograms or more daily
[unlicensed use] and use either an extended or a‘tricycling’
regimen (i.e. taking three packets of monophasic tablets
without a break followed by a shortened tablet-free interval
of four days [unlicensed use]); continue for the duration of
treatment with the interacting drug and for four weeks after
stopping.
If breakthrough bleeding occurs (and all other causes are
ruled out) it is recommended that the dose of
ethinylestradiol is increased by increments of 10 micrograms
up to a maximum of 70 micrograms daily [unlicensed use] on
specialist advice, or to use additional precautions, or to
change to a method unaffected by the interacting drugs.
Use of contraceptive patches and vaginal rings (including
concurrent use of two patches or two vaginal rings) is not
recommended for women taking enzyme-inducing drugs
over a long period.h
Long-term course (over 2 months) of rifampicin or rifabutin
An alternative method of contraception (such as an IUD) is
alwaysrecommended because they are such potent enzyme-
inducing drugs; the alternative method of contraception
should be continued for four weeks after stopping the
enzyme-inducing drug.
Antibacterials that do not induce liver enzymes
gIt is recommended that no additional contraceptive
precautions are required whencombinedoral contraceptives,
contraceptive patches or vaginal rings are used with
antibacterials that do not induce liver enzymes, unless
diarrhoea or vomiting occur. These recommendations should
be discussed with the woman.h
There had been concerns that some antibacterials that do
not induce liver enzymes (e.g. ampicillin p. 341 , doxycycline
p. 352 ) reduce the efficacy ofcombinedoral contraceptives by
impairing the bacterialflora responsible for recycling
ethinylestradiol from the large bowel. However, there is a
lack of evidence to support this interaction.
Oralprogestogen-only contraceptives interactions
Effectiveness of oral progestogen-only preparations is not
affected by antibacterials that do not induce liver enzymes.
gThe efficacy of oral progestogen-only preparations is,
however, reduced by enzyme-inducing drugs or griseofulvin
and an alternative contraceptive method, unaffected by the
interacting drug, is recommended during treatment with an
interacting drug and for at least 4 weeks afterwards.
For a short course of an enzyme-inducing drug (less than
two months), continuing the progestogen-only oral method
may be appropriate if used in combination with consistent
and careful use of condoms for the duration of treatment and
for four weeks after stopping the enzyme-inducing drug.hParenteralprogestogen-only contraceptives interactions
Effectiveness of parenteral progestogen-only contraceptives
is not affected by antibacterials that do not induce liver
enzymes.gThe effectiveness of intramuscular
norethisterone injection and intramuscular and
subcutaneous medroxyprogesterone acetate injections is not
affected by enzyme-inducing drugs and they may be
continued as normal during courses of these drugs.
Effectiveness of the etonogestrel-releasing implant p. 511
may be reduced by enzyme-inducing drugs or griseofulvin
and an alternative contraceptive method, unaffected by the
interacting drug, is recommended during treatment with the
interacting drug and for at least 4 weeks after stopping.
For a short course of an enzyme-inducing drug, if a
change in contraceptive method is undesirable or
inappropriate, continued contraception with the implant
may be appropriate if used in combination with consistent
and careful use of condoms for the duration of treatment and
for 4 weeks after stopping the enzyme-inducing drug.hBNFC 2018 – 2019 Contraception 497
Genito-urinary system7