No, this post will not be about the federal law which keeps pseudoephedrine products behind the pharmacy counter. For the record, I honestly couldn't care less about the methamphetamine problem in this or any other country. If someone wants to take the initiative to buy 100 boxes of sudafed and cook up some meth in their basement, it doesn't bother me in the least bit. After all, I'm not the one that's developing a life threatening addiction for the sake of getting high. I'm not the one throwing my life away. Moreover, alcohol is a far bigger problem in this country than methamphetamine ever could be, but no one is trying to make alcohol illegal. If you want to fight a war on drugs, then I propose throwing alcohol in there for the sake of consistency.
When a customer comes to the counter with nasal congestion and wants some advice about which product to take, we always ask one question: "Do you have high blood pressure or take medication to treat high blood pressure?" If the patient answers yes, we automatically rule out the only OTC option that's effective for nasal congestion. In fact, it's one of the only OTC drugs that actually is effective at all.
With every new study that comes out, dextromethorphan looks less and less effective at suppressing cough. Guaifenesin has never really been proven to break up chest congestion. Ask allergy sufferers how well loratidine (Claritin) works for them, and you'll meet some pretty disappointed people. Pseudoephedrine really does work to relieve nasal congestion though, which is more than we can say about its replacement, phenylephrine.
If it's effective, then why are we so quick to rule it out for people taking antihypertensives? The answer we're taught to give is that pseudoephedrine can raise your blood pressure, which would be bad for a person that already has high blood pressure. However, I contend that a short, as needed course of pseudoephedrine probably isn't any more harmful than a stressful day at work. Moreover, someone who's blood pressure is well controlled by antihypertensive medication is at as much risk as someone who doesn't have high blood pressure and doesn't take any medication.
If you really look at the data, pseudoephedrine's effect on blood pressure isn't all that alarming. This patient counseling point is pounded into us from the very beginning of pharmacy school as if taking pseudoephedrine could send someone into a hypertensive crisis. In reality, it raises blood pressure by a few points on average, and its effect certainly isn't powerful enough to offset someone taking one or several antihypertensive medications.
If you really want to get serious about all these OTC interactions, we can include some we usually don't talk about. For example, someone taking beta blockers such as metoprolol or carvedilol for high blood pressure or chronic heart failure probably shouldn't be taking antihistamines either. Both metoprolol and carvedilol are metabolized by cytochrome P450 2D6, and most over the counter first generation antihistamines (i.e. diphenhydramine) inhibit 2D6, which would raise the levels of those drugs in their systems and put them at risk for a bradycardic episode. That never seems to stop us from recommending these products to people taking metoprolol or carvedilol, and rightfully so because the risk just isn't that great.
It's the same with pseudoephedrine. For the vast majority of cold sufferers the risk of a short, as needed course of pseudoephedrine causing an adverse event is very small. Therefore, when these situations come up, I usually ask patients if their high blood pressure is being well-controlled by their medication. If they say yes, I ask them if they check their blood pressure regularly and ask what the results tend to be. If they say that every time they go to their doctor's office, their blood pressure comes out 120/80 (or close to it), then I tell them that while pseudoephedrine can possibly raise blood pressure a small amount, using it for a few days on an as needed basis is generally safe. However, if the nasal congestion lasts more than 3 days, and/or you're not getting any relief from the pseudoephedrine, contact your doctor.
Of course, if the person has high, uncontrolled blood pressure, CHF, or poorly controlled diabetes, I wouldn't recommend pseudoephedrine products. However, in the other cases I mentioned, I feel like pharmacists are too quick to rule out one of the few effective OTC cold medications.