Presentation on theme: "Oral Contraceptives and GeneMedRx Christopher E. Stephens UW Doctor of Pharmacy Candidate 2007 July 26 th 2006."— Presentation transcript:
Oral Contraceptives and GeneMedRx Christopher E. Stephens UW Doctor of Pharmacy Candidate 2007 July 26 th 2006
Why I chose oral contraceptives Oral contraceptives are a fact of life for a large portion of the population that a pharmacist will encounter. Men, even male medical practitioners, often feel uncomfortable talking to women about contraception, and women often have less confidence that a man can answer their questions on the topic.
Why I chose oral contraceptives I want to be able to serve all of my patients, not shy away from a topic because I am unfamiliar with it, or come off as uneducated to my female patients. Nothing in life is to be feared. It is only to be understood. It is only to be understood. Marie Curie
Whats in an oral contraceptive? Oral contraceptives contain either a combination of estrogen and progestin or a progestin alone. Estrogen, usually as ethinyl estradiol, prevents the development of follicles by suppressing FSH; increases the effect of progestins; and stabilizes the endometrial lining. Progestins block ovulation by suppressing the LH surge and contributes to contraception by thickening cervical mucus
What is GeneMedRx? GeneMedRx is a software tool designed to help physicians predict whether or not drugs are safe and effective for patients. 1 1 http://www.genemedrx.com/public/home.html
How does it work? GeneMedRx is designed to predict drug interactions based upon how drugs are metabolized and what enzymes or transporters are usually involved in that metabolism. The program can take into account a persons genetics, the genes that affect each persons ability to make specific enzymes or express transporters, in predicting these drug interactions. If you do not know your genetic information, Genelex, the company that created GeneMedRx, offers genetic testing
Contraceptive Drug Interaction A search of PubMed was conducted using the keywords Contraceptive Drug Interaction 692 results were found that were accessible through the University of Washington. 100 of those summaries were reviewed 41 Abstracts were evaluated 31 Full text articles were selected
Sixty Five Drug Interactions were Identified and processed through GeneMedRx
72% of all information found was already being predicted by the GeneMedRx program!
Keeping GeneMedRx Current The most recent article suggesting a drug interaction was only published Mar 2006 Sixty five potential interactions were found on PubMed and this translated into over 30 new notes added to GeneMedRx to ensure that all drug/drug, drug/class and drug/enzyme interactions were updated.
Oral contraceptives and GeneMedRx Estrogen metabolized by: Estrogen Inhibits: Estrogen Induces: Progestin metabolized by: some Progestins Inhibit: UGT1A1CYP3A…CYP1A2CYP1A2CYP2C9CYP2C19CYP2B6CYP3A…UGT1A4CYP2C9CYP2C19CYP3A…CYP2C9CYP2C19CYP3A…
Beneficial Metabolism Estrogen increases the effect of progestins; as you can see from the previous table, progestins are metabolized by the CYPs 2C9, 2C19, and the 3A series, but estrogen inhibits those same enzymes, this means that progestins are not metabolized as quickly in the presence of estrogen and therefore have more time to act in the body.
When interactions go bad Estrogens ability to boost progestins is beneficial, but that same trait turns out to be harmful when the drug that is inhibited has side effects or toxicities. If ethinyl estradiol is given with the drug clozapine, which is metabolized in part by 3A4, the concentrations of clozapine increase in the body and can lead to increased side effects, including drowsiness, tremor or nausea.
Drugs that may have increased plasma levels because of oral contraceptives CaffeineCarisoprodolChlorpromazineClozapineNaratriptanOmeprazoleTizanidine Dose reduction may be required for these medications while on contraceptives
Drugs that may have decreased plasma levels from oral contraceptives DextromethorphanLamotrigine Valproic acid Warfarin Dose adjustments may be required for these medications while on oral contraceptives
Drugs that can decrease the effectiveness of oral contraceptives Antibiotics Carbamazepine FelbamateGriseofulvin Kaletra®Lamotrigine NelfinavirNevirapine OxcarbazepinePhenobarbitol Phenytoin Rifampin RitonavirSt. Johns Wort TegaserodTopiramate Alternate methods of contraception should be suggested while on these medications.
Culprits and Victims The ethinyl estradiol component of oral contraceptives was the primary culprit/victim in most drug interactions; 46 of the 65 drug interactions found involved ethinyl estradiol! The drug class most often the culprit/victim of drug interactions were the anticonvulsant drugs, such as topiramate, lamotrigine and phenobarbital.
So what does this mean? A decrease in the efficacy of oral contraceptives was the primary result of many drug interactions, leading to unplanned pregnancies. Increased toxicity or side effects of some medications was another potential drug/drug interaction problem A third problem is sub-therapeutic doses being given because the OC is causing a decrease in the levels of treatment drug; for example, when dosing lamotrigine and OCs.
So what can we do? Practitioners should be aware of all medications that their patients are taking and not forget to or feel uncomfortable with inquiring about contraception. Patients should be sure to tell their doctor/pharmacist all of the drugs that they are taking, including contraceptives or herbal products. The one drug you forget to mention will probably be the one that causes problems!
How can GeneMedRx help? The list of drugs that exist and can potentially interact is long and keeps growing. New studies are being done and new articles are published frequently that tell of new drugs or new interactions. The GeneMedRx program is useful in actually predicting these interactions before they occur and thereby informing the patient/practitioner before a drug interaction may occur. The program also provides notes about and references to articles that list specific drug interactions.
Learn more about GeneMedRx http :// www.genemedrx.com/demo.html www.genemedrx.com/demo.html
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