Contraceptives, interactions Flashcards
COC, PO-oral contraceptives, contraceptive patches, vaginal rings, subnormal implants and EHC can be considerably reduced by interaction with drugs that are enzyme INDUCERS e.g. …. so additional or alternative methods are needed
carbamazepine, eslicarbazepine, oxcarbazepine, phenytoin, phenobarbital, primidone, topiramate
St Johns wort
rifampicin, ritonavir, efavirenz
What may be more suitable for pt with HIV or at risk of it?
condom + long acting method e.g. injectable
who should you seek advice on the possibility of interaction with antiretroviral drugs in pt with HIV and needing contraception
HIV specialists
Can you use St Johns Wort with contraception
avoid with all forms of hormonal contraception
what is the preferred method of contraception in females taking teratogenic or potentially teratogenic drug that is an enzyme inducer (e.g. SV, 3Ps1C, ritovanir, rifampicin, efavirenz)
(2)
Cu-IUD or PO-IUD (levonorgestrel)
In females taking a teratogenic or potentially teratogenic drug that is an enzyme inducer, or if an enzyme-inducing drug is also being taken with a teratogen or potential teratogen, the preferred method of contraception is a copper intra-uterine device (IUD) or a progestogen-only IUD. Can a progestogen-only injectable (e.g. MDP) also be used?
Yes but has to be in combo with reliable use of condoms
What are some contraceptive methods that are unaffected by enzyme inducers & how long do they need to be continued for?
Cu IUD
PO IUD
PO injectable contraceptive e.g. MDP
continue for duration of treatment and for 4 weeks after stopping
when can you consider continuing hormonal contraception whilst taking enzyme inducing drug (NOT RIFAMPICIN OR RIFABUTIN)
short term use (2 months or less) if used in combination with consistent and careful use of condoms for duration of treatment and for 4 weeks after stopping enzyme inducer
True or false - you can use a monophonic combined oral contraceptive containing ethinylestradiol at a higher daily dose (unlicensed) to be used either continuously or tricycled (3 packed of tabs without a break followed by a shorted tablet free interval of 4 days) (unlicensed) when taking enzyme inducing drug (except rifampicin or rifabutin)
(and what to do if breakthrough bleeding.)
true (continued use, over 2 months) only in exceptional circumstances. Must continue for duration of treatment with interacting drug & for 4 weeks after stopping. However contraceptive effectiveness is not guaranteed. If breakthrough bleeding occurs (and all other causes rules out), use additional precautions or change contraception to a method that is unaffected by the interacting drugs.
If you are taking rifampicin or rifabutin, what contraceptives must you have
ALWAYS a method that is UNAFFECTED By enzyme inducers because they are such POTENT inducers!!
Continue for 4 weeks after stopping inducer
A patient is on ritonvair (HIV protease inhibitor). Can they still take CHC?
Despite it being an inducer, yes. Not expected to affect efficacy of CHC, but caution is required because increase risk of SE may impact adherence
CHC + lamotrigine - interaction
Lamot can reduce efficacy of CHC - reliable use of condoms needed
However CHC can decrease lamb conc - reduced efficacy? e.g. seziure control!!
If CHC unavoidable, consider increasing lamot dose + monitoring lamot conc.
what regimen of CHC would you consider using when taking lamotrigine
A continuous combined hormonal contraceptive regimen (with no hormone-free interval) could be used to avoid cyclical changes in lamotrigine concentrations [unlicensed use]
this is because CHC can decrease lamot conc which can result in reduced efficacy (e.g. seizure control)
oral PO contraceptive interactions with enzyme inducers
what alternative methods
efficacy of oral PO preps is reduced by enzyme inducers
alternative contraceptive method e.g. Cu-IUD, PO IUD, PO injectable e.g. MDP recommended during treatment and for 4 weeks after discontinuing
Ritonavir is an enzyme inducer - can you take oral PO contraceptives?
despite it being an inducer, concurrent use of HIV protease inhibitors boosted with ritonavir are not expected to affect efficacy of oral PO contraceptives, but may increase their conc
no extra precautions are needed in those taking HIV protease inhibitors boosted with ritonavir
For short term use of enzyme inducing drug (less than 2 months), can you continue PO oral method even though there is an interaction and efficacy is reduced??
For short-term use of an enzyme-inducing drug (less than 2 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 4 weeks after stopping the enzyme-inducing drug.
interactions with lamotrigine and PO oral contraceptives
- is there an interaction? any additional protection needed? which one may increase lamot conc? important advice for pt?
It is possible that lamotrigine could reduce the efficacy of progestogen-only oral contraceptives, therefore the additional reliable use of condoms is recommended.
Desogestrel might increase lamotrigine concentrations, but evidence for other oral progestogen-only contraceptives is lacking.
Patients should be advised to be vigilant for signs of lamotrigine toxicity if starting progestogen-only contraceptives and consideration given to monitoring lamotrigine concentrations on stopping the contraceptive.
T or F - 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
true
Is the effectiveness of etonogestrel releasing subdermal implant reduced by enzyme inducers?
yes
alternative contraceptive method that is unaffected by interacting drug (Cu-IUD, PO-IUD, PO-injectable) Is recommended during treatment and for at least 4 weeks after stopping
parenteral (incl subdermal) PO contraceptive interactions
for a short course of enzyme inducing drug, if change in contraceptive method is undesirable or inappropriate what can you do
+ info re ritonavir
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.
Note that despite ritonavir being an enzyme inducer, the FSRH suggests that concurrent use of HIV-protease inhibitors boosted with ritonavir are not expected to affect the efficacy of the etonogestrel implant but might increase etonogestrel concentrations. They therefore state that no extra precautions are needed in those taking HIV-protease inhibitors boosted with ritonavir.
parenteral (incl subdermal) PO contraceptive interactions
does lamotrigine interact?
It is possible that lamotrigine could reduce the efficacy of the progestogen-only subdermal implant, therefore the additional reliable use of condoms is recommended.
Contraceptive effectiveness of progestogen-only injectable contraceptives is not expected to be affected by lamotrigine, however progestogen-only contraceptives might increase lamotrigine concentrations.
Patients should be advised to be vigilant for signs of lamotrigine toxicity if starting progestogen-only contraceptives and consideration given to monitoring lamotrigine concentrations on stopping the contraceptive.
do enzyme inducers affect EHC
The effectiveness of levonorgestrel and ulipristal acetate could be reduced in females taking enzyme-inducing drugs (and for at least 4 weeks after stopping).
A copper IUD can be offered instead.
what EHC should you give to a patient if they are on an enzyme inducer
The effectiveness of levonorgestrel and ulipristal acetate could be reduced in females taking enzyme-inducing drugs (and for at least 4 weeks after stopping). A copper IUD can be offered instead.
if copper IUD is declined or unsuitable in a pt who needs EHC and they take enzyme inducer, what should you do
+ advice for ritonavir
double dose levonorgestrel
if levonorgestral unsuitable, consider standard dose uliprostal
advice female that effectiveness of EHC when enzyme inducers are taken if unknown
Note that despite ritonavir being an enzyme inducer, the FSRH suggests that concurrent use of HIV-protease inhibitors boosted with ritonavir do not affect the efficacy of levonorgestrel emergency hormonal contraception but might increase levonorgestrel concentrations. They therefore do not extend the advice for enzyme inducers to HIV-protease inhibitors boosted with ritonavir.
which EHC is affected by drugs that increase gastric pH e.g. PPIs etc
and what to do in pt taking these
The effectiveness of ulipristal acetate for emergency contraception in females using drugs that increase gastric pH is unknown. A copper IUD or levonorgestrel can be offered instead. If these are unsuitable, ulipristal acetate can be offered, but it is possible that effectiveness could be reduced.
hormonal contraception should NOT be NEWLY inititated in a pt until how many days AFTER ulipristal is taken as EHC and why?
do not initiate until 5 days after admin
this is bc contraceptive effect of ulipristal will be reduced
tell them to use careful and consistent use of condoms
how soon after ulipristal is given can a female who uses regular COC restart?
Females on a regular combined oral contraceptive may in certain circumstances be able to restart regular contraception immediately after administration of ulipristal acetate if they have have missed contraception within the first week of restarting after a scheduled hormone-free interval, and have taken ulipristal acetate as emergency contraception; they must use condoms reliably or abstain from intercourse for 7 days until contraception becomes effective
when a progestrogen including levonorgestrel EHC is given 7 days before or 5 days after admin of ulipristal as EHC, what effect may it have
the contraceptive effect of ulipristal acetate may be reduced.
true or false - do abx that DO NOT induce liver enzymes e.g. ampicillin, doxy reduce the efficacy or COC by impairing the bacterial flora responsible for recycling ethinylestradiol from the large bowel?
No evidence !
