Q: I am 22 years old and am taking a low dose oral contraceptive. I understand that taking certain other medications can interfere with the pill, increasing my chance of getting pregnant. Can you tell me which ones I need to be careful with? Should I take two pills on the days that I take any of these other drugs?
A: Oral contraceptives are metabolized in the liver, therefore other medications that are metabolized in a similar way may reduce blood levels of the pill to the point that there is more probability of becoming pregnant. If you are taking one of these substances, you should not take higher doses of the oral contraceptive since that could lead to greater side effects.
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Instead, it is better to use some other form of contraception in addition while you are taking the other drugs and for a few days after discontinuing them. If the other medication is something you require indefinitely, you may wish to consider alternative forms of birth control, or perhaps a higher dose pill would do. If this is needed you will get a clue because of breakthrough bleeding usually at mid-cycle.
The main medications to cause these problems are anticonvulsants that are used in the treatment of epileptic seizures. The most commonly used are Phenytoin, Phenobarbitone and carbemazepine (Tegretol). Valproic acid, an anti-seizure drug also sometimes used to stabilize people suffering from bipolar disorder, does not have this effect.
You need to be careful with the antifungal drug Griseofulvin and with some broad-spectrum antibiotics such as tetracycline. The anti-AIDS drug Nevirapine can also cause problems, so women suffering from AIDS should not use oral contraceptives as the primary method of birth control.
Theoretically, some antacids and absorbent medications such as Tums and Kaopectate could interfere with oral contraceptive efficiency, but there is no firm evidence that this is the case. Also on a theoretical level, since vitamin C and acetaminophen (Tylenol) may increase the plasma concentrations of the Pill, there could be a rebound effect if these substances are stopped suddenly.
You may also have to use caution with certain herbs. St. John’s Wort sometimes used for depression, and red clover, may lead to dangerous interactions.
Re: Letters about dietary supplements for arthritis
I have received several letters from people offering suggestions for the person who wrote to me asking for herbal and dietary remedies for arthritis. In a previous column I mentioned glucosamine, chondroitin and green tea.
As far as I could discover, all the other brand-named supplements, such as JointRX, contained mainly glucosamine, sometimes mixed with orange juice and ginger.
Ginger is supposed to have an anti-inflammatory effect like red pepper, but it would be much cheaper to buy either of these spices separately.
Apple cider vinegar was another suggestion. Again, I do not see why this is any better than regular vinegar except that it tastes a little better. There is no proof that it works but you can always add a little to your cooking and see if it helps. You don’t have to drink it straight.
Clare Rowson is a medical doctor with a practice near Belleville, Ont. Her columns are intended for general information only. Individuals are encouraged to also seek the advice of their own doctor regarding medical questions and treatments.
