Cynthia R. Biron, RDH
Now that cimetidine (Tagamet) and famotidine (Pepcid) are available without prescription, many more of our patients may be taking them. Should we be concerned that these drugs could interact with those used in dentistry? Will they require us to alter our treatment plans? Will our patients remember to tell us they are taking them if they don`t consider over-the-counter drugs to be a concern during dental treatment?
These questions and more are being asked by dental-health professionals. It has been difficult enough to get patients to tell us about aspirin and cold remedies, and now we have another category of drugs that is readily available without prescription. That category of drugs is known as histamine H2 antagonists.
What are histamine H2 antagonists?
Histamine H2 antagonists block histamine at the H2 receptors of gastric cells. All the drugs in this category inhibit gastric secretions. Two other drugs in this category are still only available by prescription. They are ranitidine (Zantac) and nizatidine (Axid).
All of these drugs alleviate the symptoms of ulcers and prevent complications in ulcer disease. Since all of the drugs in this category are effective in inhibiting gastric secretions, it is unlikely that an ulcer that does not heal with one would heal with any of the others. Each of the four H2 antagonists is produced by different pharmaceutical companies. None of the drugs is available in the generic form over the counter.
The labeled uses for all H2 antagonists include duodenal ulcer treatment and maintenance, gastroesophageal reflux disease, erosive esophagitis, and pathological hypersecretory conditions. Unlabeled uses of both Tagamet and Pepcid include prophylaxis of stress ulcers and prevention of aspiration pneumonitis. Of the four H2 antagonists, only Tagamet has the labeled use of preventing upper G.I. bleeding in critically ill patients.
Tagamet has the most unlabeled uses of any of the group. Some unlabeled uses were discovered by accident in patients who were taking Tagamet for their ulcers and got relief from other conditions at the same time. The unlabeled uses include treatment of hyperparathyroidism, secondary hyperparathyroidism in hemodialysis patients, tinea capitis, herpes virus infection, hirsute women, chronic idiopathic urticaria, dermatological anaphylaxis, acetaminophen overdose, and dyspepsia.
Comparing Tagamet and Pepcid
There is a great deal of competition between the two drugs that are available without a prescription. The advertising in magazines and on television has consumers wondering which is the better drug. Each drug has its own separate benefits, and the wise consumer will do a little research or, better still, discuss the drugs with a physician before purchasing either medication.
While Tagamet has been FDA-approved since 1977, Pepcid was approved in 1986. Tagamet has many more unlabeled uses than Pepcid, but Tagamet has more drug interactions by decreasing hepatic metabolism of numerous drugs.
Because Tagamet inhibits the cytochrome P-450 oxidase system, it reduces the metabolism of drugs that utilize the P-450 pathway. Benzodiazepines (except loraxepam, oxazepam, and temazepam), caffeine, calcium channel blockers, carbazepine, chloroquine, labelatol, lidocaine, metoprolol, metronidazole, moricizine, pentoxifyline, phentoin, propafenone, propranolol, quinidine, quinine, sulfonylureas, theophyllines (except dyphylline), tramferene, tricyclic antidepressants, and warfarin could result in increased pharmacological effects or toxicity if taken concomitantly with Tagamet. The pharmacological effects of ferrous salts, indomethacin, ketoconazole, and tetracyclines may be decreased by Tagamet as it decreases their absorption.
The healing rates of duodenal ulcers is similar in both drugs. Pepcid is 30 to 60 times more potent than Tagamet on a molar basis in controlling acid secretions but the potency does not place Pepcid at an advantage in healing duodenal ulcers.
The therapeutic dosages of each drug provides the similar healing effect in four- and eight-week courses of treatment. One thousand milligrams per day of Tagamet healed 60 to 84 percent of ulcers in patients treated in a four-week course; 40 mg. per day of Pepcid healed 67 to 77 percent of ulcers in patients treated in a four-week course. Both drugs taken in their therapeutic doses healed ulcers of 85 to 95 percent of patients treated in an eight-week course.
Adverse reactions shown in clinical trials included headaches in 1 percent of patients taking Tagamet and 4.7 percent of patients taking Pepcid. Numerous adverse affects of various types have occurred with both drugs since they have been approved. But not all adverse effects have been reported or well established through studies. Fatigue, dizziness, confusional states, impotence and G.I. disturbances have occurred rarely or in up to 1 percent of patients studied in treatment with both drugs.
Our concerns in dentistry really are more in the use of Tagamet, due to its drug interactions with so many of the drugs used in dentistry. Lidocaine and benzodiazepines are used very frequently in dentistry, and toxic levels of those drugs could be quite serious.
The antibiotics and antifungal agents often prescribed in dentistry will not be properly absorbed in patients taking Tagamet. While patients were more likely to tell us they were on Tagamet when it was prescribed, they will be more likely to view it as less potent or innocuous now that it is available without a prescription.
If our patients are taking anticoagulants, we will be more concerned about invasive treatment. Even when a physician is consulted due to a history of their patient taking anticoagulants, they frequently say the patient only needs to stop taking their anticoagulant the day of the appointment. If the patient has been taking Tagamet, they might still have an increased prothrombin time and be at risk for uncontrollable bleeding.
The antacid effects of both Tagamet and Pepcid will tempt acid-indigestion sufferers to try the drugs without consulting their physician. Patients taking other medications that are decreased in effectiveness when taken with Tagamet such as calcium channel blockers, digoxin or other cardiac drugs could be at risk for a medical emergency if they are also very apprehensive about their dental appointment.
Perhaps we need to add a new question to the patient medical history: OWhat over-the-counter medications do you take now or on occasion?O
Cynthia R. Biron, RDH, is chair of the dental hygiene program at the Tallahassee Community College. She is also a certified emergency medical technician.