ABSTRACT
Watch for toxic effects of ciclosporin
DANAZOL TACROLIMUS Cases of ≠ tacrolimus levels Uncertain Watch for early features of tacrolimus toxicity
DANAZOL ANTICOAGULANTS – ORAL Possible ↓ anticoagulant effect Uncertain Monitor INR at least weekly until stable
DANAZOL ANTIEPILEPTICS – CARBAMAZEPINE
≠ plasma concentrations of carbamazepine, with risk of toxic effects
Inhibition of carbamazepine metabolism
Watch for toxic effects of carbamazepine
DANAZOL OESTROGENS ↓ efficacy of both danazol and oestrogen contraceptives
Uncertain; possibly competition for same receptors
Use alternative forms of contraception
ERGOMETRINE ➣ Drugs Acting on the Nervous System, Antimigraine drugs
FEMALE HORMONES
OESTROGENS
OESTROGENS REDUCED EFFICACY OF OESTROGENS
OESTROGENS 1. ANTIBIOTICS – ampicillin, cephalosporins, chloramphenicol, clindamycin, erythromycin, metronidazole, sulphonamides, tetracyclines 2. ANTIPROTOZOALS – tinidazole
Reports of ↓ contraceptive effect Possibly alteration of the bacterial flora necessary for recycling ethinylestradiol from the large bowel, although not certain in every case
Advise patients to use additional contraception for the period of antibiotic intake and for 1 month after stopping the antibiotic
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3. ANTIEPILEPTICS – barbiturates, carbamazepine, oxcarbazepine, phenytoin, topiramate 4. ANTIFUNGALS – griseofulvin, terbinafine 5. ANTIVIRALS – nelfinavir, nevirapine, ritonavir 6. CNS STIMULANTS – modafinil
↓ Induction of metabolism of oestrogens. Modafinil is moderate inducer of CYP1A2 in a concentration-dependent manner
Advise patients to use additional contraception for the period of intake and for 1 month after stopping co-administration of these drugs (4-8 weeks after stopping rifabutin or rifampicin). Barrier methods are necessary to prevent transmission of infection from patients with HIV. Avoid co-administration of oestrogens with St John’s wort
OESTROGENS 1. ANTICANCER AND IMMUNOMODULATING DRUGS – mycophenolate 2. ANTIEMETICS – aprepitant 3. ANXIOLYTICS AND HYPNOTICS – BZDs, meprobamate 4. PROTON PUMP INHIBITORS – lansoprazole
Possible altered efficacy of contraceptive; reports of breakthrough bleeding when BZDs or meprobamate were co-administered with oral contraceptives
Unclear Clinical significance uncertain. It would seem to be wise to advise patients to use an alternative form of contraception during and for 1 month after stopping co-administration of these drugs
OBSTETRICS AND GYNAECOLOGY FEMALE HORMONES Oestrogens
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Mechanism Precautions
KETOCONAZOLE, POSACONAZOLE, VORICONAZOLE
of pill cycle disturbances 2-3 weeks after the start of the pill cycle, delayed bleeding and pregnancy. Effects of either or both of oestrogen excess and progestogen excess may occur (migraine headaches, thromboembolic episodes, breast tenderness, bloating, weight gain)
The metabolism of oral contraceptives is complex, dependent on composition, constituents and doses. Ethylene oestradiol (EE), a common constituent, as well as progestogens are substrates of CYP3A4, which is inhibited by itraconazole. The inhibition of ethinylestradiol and progestogens could lead to effects of oestrogen and progestogen excess. Triazole antifungals inhibit the biotransformation of steroids, and such an ≠ may cause delay of withdrawal bleeding
Due to the complex metabolic pathways of oral contraceptives, dependent on constituents, doses and the reported adverse effects during concomitant use, it is advisable to avoid the use of azole antifungals and advise alternative methods of contraception
OESTROGENS INCREASED EFFICACY OF OESTROGENS
OESTROGENS 1. ANTICANCER AND IMMUNOMODULATING DRUGS – ciclosporin, tacrolimus 2. CALCIUM CHANNEL BLOCKERS – nicardipine, nisoldipine, verapamil 3. DIURETICS – spironolactone
Risk of gynaecomastia Inhibition of 2-hydroxylation or 17-oxidation of oestradiol in the liver, causing ≠ oestradiol pool in the body
Watch for gynaecomastia and warn patients
OESTROGENS – ESTRADIOL, POSSIBLY ETHINYLESTRADIOL
GRAPEFRUIT JUICE ≠ efficacy and ≠ adverse effects of oestrogens
Oral administration only. ≠ bioavailability and ↓ presystemic metabolism. Constituents of grapefruit juice irreversibly inhibit intestinal cytochrome CYP3A4. Transport via P-gp and MRP-2 efflux pumps is also inhibited
Monitor for ≠ side-effects
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OBSTETRICS AND GYNAECOLOGY FEMALE HORMONES Oestrogens
Etoricoxib inhibits sulphotransferase activity
Consider using a formulation with a lower dose of ethinylestradiol
OESTROGENS OPIOIDS Effect of morphine may be ↓ by combined oral contraceptives
≠ hepatic metabolism of morphine Be aware that the morphine dose may need to be ≠. Consider using an alternative opioid such as pethidine
OESTROGENS ANTICANCER AND IMMUNOMODULATING DRUGS – ciclosporin, corticosteroids, tacrolimus
Possibly ≠ plasma concentrations of these immunomodulating drugs
Inhibition of metabolism Monitor blood levels of these drugs; warn patients to report symptoms such as fever and sore throat
OESTROGENS ANTICOAGULANTS – ORAL ≠ anticoagulant effect Uncertain at present Oestrogens are usually not recommended in patients with a history of thromboembolism; if they are used, monitor INR closely
OESTROGENS ANTIDIABETIC DRUGS Altered glycaemic control Uncertain at present Monitor blood glucose closely
OESTROGENS 1. ANTIHYPERTENSIVES AND HEART FAILURE DRUGS 2. BETA-BLOCKERS 3. CALCIUM CHANNEL BLOCKERS 4. NITRATES
↓ hypotensive effect Oestrogens cause sodium and fluid retention
Monitor BP at least weekly until stable; the routine prescription of oestrogens in patients with ≠ BP is not advisable
OESTROGENS ANTIEPILEPTICS – LAMOTRIGINE
↓ lamotrigine levels ≠ metabolism Monitor levels
OESTROGENS ANTIPARKINSON’S DRUGS – ROPINIROLE, SELEGILINE
≠ levels of ropinirole and selegiline Inhibition of metabolism (possibly N-demethylation)
Watch for early features of toxicity (nausea, drowsiness) when starting oestrogens in a patient stabilized on these dopaminergics. Conversely, watch for a poor response to them if oestrogens are stopped
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Mechanism Precautions
↓ clearance of theophylline in a
dose-dependent manner Be aware; watch for features of theophylline toxicity and measure levels
OESTROGENS DANAZOL ↓ efficacy of both danazol and oestrogen contraceptives
Uncertain; possibly competition for the same receptors
Use alternative forms of contraception
OESTROGENS SOMATROPIN Possible ↓ efficacy of somatropin Uncertain ≠ dose of somatropin may be needed OESTROGENS VASODILATOR
ANTIHYPERTENSIVES Risk of hyperglycaemia when diazoxide is co-administered with combined oral contraceptives
Additive effect; both drugs have a hyperglycaemic effect
Monitor blood glucose closely, particularly with diabetics
PROGESTOGENS
PROGESTOGENS REDUCED EFFICACY OF PROGESTOGENS
PROGESTOGENS 1. ANTIBIOTICS – rifabutin, rifampicin 2. ANTIDEPRESSANTS – St John’s wort 3. ANTIEPILEPTICS – barbiturates, carbamazepine, oxcarbazepine, phenytoin, topiramate 4. ANTIFUNGALS – griseofulvin, terbinafine 5. ANTIVIRALS – amprenavir, nelfinavir, nevirapine, ritonavir 6. VASODILATOR ANTIHYPERTENSIVES – bosentan
↓ progesterone levels, which may lead to failure of contraception or poor response to treatment of menorrhagia
Possibly induction of metabolism of progestogens
Advise patients to use additional contraception for the period of intake and for 1 month after stopping co-administration with these drugs. Barrier methods are necessary to prevent transmission of infection from patients with HIV. Avoid co-administration of progestogens with St John’s wort
PROGESTOGENS ANTIEMETICS – APREPITANT ↓ progestogen levels, with risk of contraceptive failure
Uncertain Advise patients to use an alternative form of contraception during and for 1 month after discontinuing the aprepitant
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OBSTETRICS AND GYNAECOLOGY FEMALE HORMONES Progestogens
AND HEART FAILURE DRUGS – ACE inhibitors, angiotensin II receptor antagonists 3. DIURETICS – potassium-sparing
Drospirenone (component of the Yasmin brand of combined contraceptive pill) is a progestogen derived from spironolactone that can cause potassium retention
Monitor serum potassium weekly until stable and then every 6 months
PROGESTOGENS ANALGESICS – OPIOIDS Gestodene ≠ effect of buprenorphine
Gestodene ↓ CYP3A4-mediated metabolism of buprenorphine
The dose of buprenorphine needs to be ↓ (by up to 50%)
PROGESTOGENS ANTICANCER AND IMMUNOMODULATING DRUGS – CICLOSPORIN
≠ plasma concentrations of ciclosporin
Inhibition of metabolism of ciclosporin
Monitor blood ciclosporin concentrations. Monitor renal function prior to concurrent therapy. Be aware that infections in immunocompromised patients carry a serious threat to life
PROGESTOGENS ANTICOAGULANTS – ORAL ↓ anticoagulant effect Uncertain at present Monitor INR closely PROGESTOGENS ANTIDIABETIC DRUGS Altered glycaemic control Uncertain at present Monitor blood glucose closely
PROGESTOGENS ANTIEPILEPTICS – LAMOTRIGINE
↓ lamotrigine levels ≠ metabolism Monitor level
PROGESTOGENS ANTIPARKINSON’S DRUGS – SELEGILINE
≠ selegiline levels Inhibition of metabolism Watch for early features of toxicity (nausea, drowsiness) when starting progestogens in a patient stabilized on these dopaminergics. Conversely, watch for a poor response to them if progestogens are stopped
NORETHISTERONE ANTIVIRALS – PROTEASE INHIBITORS
≠ adverse effects with amprenavir and atazanavir
Uncertain Watch for early features of toxicity of amprenavir and atazanavir, and adjust the dose accordingly
