GU: Contraceptives, interactions.

Question 1

What are drugs that can induce hepatic enzyme activity?

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N
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P
P
P
R
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R

Answer 1

Carbamazepine
Eslicarbazepine
Nevirapine
Oxcarbazepine
Phenytoin
Phenobarbital 
Primidone
Ritonavir 
St John's Wort
Topiramate
Rifabutin
Rifampacin 

(possibly also griseofulvin)

Question 2

Women 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 not affected by enzyme-inducers such as:

Answer 2

1. Parenteral progestogen-only contraceptives (medroxyprogesterone acetate and norethisterone)
2. Intra-uterine devices (levonorgestrel).

Question 3

Women 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 and norethisterone) or intra-uterine devices (levonorgestrel; see also Contraceptives, non-hormonal).

This should be continued for how long?

Answer 3

The duration of treatment and for four weeks after stopping.

Question 4

What are the parenteral progestogen-only contraceptives which are not impacted by enzyme-inducers?

Answer 4

Medroxyprogesterone acetate and norethisterone.

Question 5

For a short course (2 months or less) of an enyme-inducing drug, contraception can be managed how?

Answer 5

Continuing 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.

Question 6

For long-term course (over 2 months) of an enzyme-inducing drug (except rifampicin or rifabutin) or a course of griseofulvin, how should contraception be managed?

Answer 6

1. Use of monophasic combined oral contraceptive at a dose of ethinylestradiol 50micrograms or more daily [unlicensed use] and use either an extended or a ‘tricycling’ regimen (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.

Question 7

What is the minimum dose of ethinylestradiol recommended for contraceptives in patients taking enzyme-inducing drugs?

Answer 7

At least 50microgram ethinylestradiol daily.

Question 8

What is ‘tricycling’?

Answer 8

Taking three packets of monophasic tablets without a break followed by a shortened tablet-free interval of four days (unlicensed).

Question 9

For how long after treatment cessation of an enzyme-inducing drug should extra precautions be used?

Answer 9

four weeks.

Question 10

If breakthrough bleeding occurs with use of ethinylestradiol (minimum 50mcg) daily and an enzyme-inducing drug, what is recommeneded?

Answer 10

The dose of ethinylestradiol should be increased by increments of 10micrograms up to a maximum of 70micrograms daily on specialist advice, or to use additional precautions, or to change to a method unaffected by the interacting drugs.

Question 11

What are the two most potent enzyme-inducing drugs, for which an alternative method of contraception (such as an IUD) is always recommended?

Answer 11

Rifampicin and rifabutin.

Rifampacin: TB, leprosy and legionnaire’s disease.

Rifabutin: TB, prevent and treat Mycobacterium avium complex. Alternative to rifampicin in people with HIV/AIDs on antiretrovirals.

Question 12

Is the effectiveness of the etonorgestrel-releasing implant impacted by enzyme-inducing drugs?

Answer 12

Yes

Question 13

What options are there for EHC in people taking enzyme-inducing drugs?

Answer 13

Effectiveness of levonorgestrel and ulipristal acetate is reduced in women taking enzyme-inducing drugs or griseofulvin.

A copper intra-uterine device can be offered instead.

If copper intra-uterine device is declined or unsuitable, the dose of levonorgestrel should be increased.

Question 14

Regular hormonal contraception should not be newly initiated in a patient until how many days after administration of ulipristal acetate as emergency hormonal contraception?

Answer 14

At least 5 days, can cause reduced effectivness of ulipristal acetate.

Question 15

Which type of EHC can be used more than once in the same cycle?

For the one that cant, why is this?

Answer 15

Ulipristal acetate can be used as EHC more than once.

The manufacturer advises that the use of levonorgestrel as EHC more than once in the same cycle is not advisable due to increased risk of side-effects.

Question 16

Levonorgestrel should not be used as emergency hormonal contraceptive within how many days of administration of Ulipristal acetate (as emergency hormonal contraception), the contraceptive effect of ulipristal acetate may be reduced by progestogens.

Answer 16

5

Question 17

Ulpristal acetate is not recommended for use in women who have severe asthma treated with what?

Why?

Answer 17

Ulipristal acetate is not recommend for use in women who have severe asthma treated by oral corticosteroids, due to the antiglucocorticoid effect of ulipristal acetate.