Tetracycline with oral contraceptives

The effects of warfarin may increase when administered with acetaminophen, NSAIDs, beta blockers, disulfiram, isoniazid, chloral hydrate, loop diuretics, aminoglycosides, cimetidine, tetracyclines, and cephalosporins. Oral contraceptives, ascorbic acid, barbiturates, diuretics, and vitamin K decrease the effects of warfarin. Because die effects of warfarin are influenced by many drugp, die patient must notify die nurse or die primary healdi care provider when taking a new drug or discontinuing... 

The effects of the progestins are decreased when administered with anticonvulsants, barbiturates, or rifampin. Administration of the penicillins or tetracyclines with the oral contraceptives decreases the effects of the oral contraceptives. 

Tetracycline Tetracycline injections have an acid pH. Incompatibility may reasonably be expected with alkaline preparations or with drugs unstable at low pH. Care should be taken when administering tetracyclines, since chelation takes place with metal ions. Tetracyclines interact with inorganic metal ions. They should not be used with drugs that cause hepatotoxicity and nephrotoxicity (e.g., digoxin, theophylline, ergot alkaloids, methotrexate, oral contraceptives, and penicillins). 

Drug Interactions Contraceptive effects are decreased when "the pill" is taken with ANTIDIOTICS (ampicillin, isoniazid, neomycin, pen V, rifampin, sulfonamides, tetracycline) or CNS AGENTS (barbiturates, benzodiazepines, phenytoin). Contraceptives increase the effects of corticosteroids and worsen side effects of tricyclic antidepressants. Oral contraceptives decrease the effectiveness of oral anticoagulants, anticonvulsants, and oral hypoglycemic agents. 

Evidence is very limited but it has been suggested that all patients given long-term minocycline treatment should be well screened for the development of pigmentation, particularly if they are taking other drugs such as the oral contraceptives that are known to induce hyperpigmentation. Remember also that very rarely contraceptive failure has been associated with the use of minocycline and other tetracyclines, see Hormonal contraceptives + Antibacterials Tetracyclines , p.983. 

The use of a penicillin (unspecified) was implicated in 32 pregnancies in women taking an oral contraceptive (unspecified) in the adverse reactions register of the CSM in the UK for the years 1968 to 1984 (a fiuther 31 cases were attributed to other antihacterials). In an earlier review, the penicillins in 15 cases of contraceptive failure were named as ampicillin (alone or with fusidic acid, tetracycline or flncloxacillin), amoxicillin, talampicillin, phenoxymethylpenicillin (one also with oxytetracycline) and penicillin . A survey of contraceptive failure descrihed failures due to amoxicillin (16 cases), flncloxacillin, phenoxymethylpenicillin, pivampicillin (3 cases) and amoxicillin with phenoxymethylpenicillin (1 case), and a follow-up survey identified 9 further cases involving amoxicillin and one with penicillin . Another similar survey descrihed a total of 17 cases with amoxicillin and 5 cases with penicillin , and a follow-up survey identified 8 further cases with amoxicillin and 1 case with penicillin . ... 

In a dermatological practice, of 124 women taking an oral contraceptive and antibacterials (mostly tetracyclines or erythromycin), 2 became pregnant, with a calculated failure rate of 1.2%. One patient was taking long-... 

The interactions between the oral contraceptives and tetracyclines summarised here are all that have been identified in the literature. Much of the evidence is anecdotal with insufficient controls (if any). These interactions are not adequately established and the whole issue remains controversial. Bearing in mind the extremely wide use of both drugs, any increase in the incidence of contraceptive failure above the accepted failure rate is clearly very low indeed. On the other hand, the personal and ethical consequences of an unwanted pregnancy can be very serious. For this reason, the Faculty of Family Planning and Reproductive Health Care (FFPRHC) Clinical Effectiveness Unit recommends that an additional form of contraception, such as condoms, should be used while taking a short course of antibacterials that do not induce liver eiKymes, and for 7 days after the antibacterial has been stopped. See Hormonal contraceptives + Antibacterials Penicillins , p.981, for more detailed information on how to manage this interaction. 

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