Drugs reducing OC concentrations or actions
|
Drug group |
Suggestion |
|
Antacids |
Give two hours apart from OCs |
|
Antibiotics |
|
|
Griseofulvin |
Avoid courses longer than 3 months ; take Other precautions if course is less than 3 months. |
|
Riafampicin |
Do not give together at all |
|
Metronidazole |
Take a good history and inform patient of possible interaction |
|
Neomycin |
in first cycles. With history of breakthrough bleeding advise |
|
Penicillins |
additional precautions. |
|
Tetracyclines |
|
|
Anticonvulsants |
|
|
Carbamazepine |
Use sodium valproate. If other drugs necessary use very high |
|
Phenobarbitone |
dose of OC to control breakthrough bleeding. |
|
Phenytoin |
Monitor FSH and LH. |
|
Primidone |
|
|
Psychoactive drugs |
|
|
Benzodiazepines |
Or doubtful significance. |
|
Meprobromate |
Advice patient to report any problems. |
|
Tricyclic |
|
|
antidepressants |
|
|
Purgatives |
Reduce dose of purgative |
Drug increasing OC concentrations or actions
|
Drug (s) |
Suggestion |
|
Ascorbic acid (vitamin C) |
Advise slow tailingoff high doses |
|
Imidazoles except Fluconazole |
Warn patient of possible adverse effects |
|
Paracetamol |
Advise slow tailingoff high doses |
OCs increased the plasma concentration of other drugs
|
Drug (s) |
Reference |
|
Alprazolam |
Stoehr et al. (1984) |
|
Chlordiazepoxide |
Roberts et al. (1979) |
|
Cyclosporine |
Cockburn & Krupp (1989) |
|
Diazepam |
Ellinwood et al. (1984) |
|
Nitrazepam |
Jochemsen et al. (1982) |
|
Propranolol |
Kendall et al. (1984) |
|
Triazolam |
Stoehr et al. (1984) |
OCs decreased the plasma concentration of other drugs
|
Drug |
Clinical effect |
Reference |
|
Clofibric acid |
Unknown |
Miners et al. (1984) |
|
Lorazepam |
Unknown |
Abernethy et al. (1983) |
|
Morphine |
Unknown |
Watson et al. (1987) |
|
Oxazepam |
Unknown |
Abernethy et al. (1983) |
|
Paracetamol |
Unknown |
Miners et al. (1984) Mitchell et al. (1983) |
|
Temazepam |
Unknown |
Stoehr et al. (1984) |
Adapted from Drug interactions with OCs, Current Therapeutics July 1994
By Gillian M. Shenfield ( Department of Clinical Pharmacology, Royal North Shore Hospital, St Leonards, New South Wales)
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