Interactions Between Nonprescription Products and Psychotropic Medications

W. Steven Pray, PhD, DPh

Disclosures

US Pharmacist. 2007;32(11):12-15. 

In This Article

Monoamine Oxidase Inhibitor Warnings

In the late 1970s, a specific group of medications was indicated for depression or hypertension: monoamine oxidase inhibitors (MAOIs). At that time, several were actively marketed as single-entity or combination products, including pargyline (Eutonyl) and pargyline/methyclothiazide (Eutron) for hypertension and phenelzine (Nardil), tranylcypromine (Parnate), and isocarboxazid (Marplan) for depression. Eventually, selegiline (Eldepryl, Emsam) was marketed, with enhanced affinity for MAOI type B active sites. It was referred to as an MAOI "B" medication, and the older products became known as MAOI "A" medications. Eutonyl, Eutron, and Marplan are no longer marketed.

Regarding MAOI therapy, one set of precautions is paramount. MAOIs block the body's ability to metabolize tyramine, carrying a high potential for drug and food interactions. Patients prescribed MAOIs are cautioned strongly against ingestion of tyramine-rich foods and drinks, such as anchovies, certain alcoholic beverages (e.g., sherry, beer), pepperoni, salami, strong/aged cheeses, raisins, bananas, and soy sauce. Failure to observe this precaution can cause cerebral hemorrhages and severe headaches.

When the nonprescription cough/cold expert panel originally appointed by the FDA issued its report in 1976, it indicated evidence of the same type of interaction between MAOIs and oral nasal decongestants (e.g., pseudoephedrine, phenylephrine, phenylpropanolamine).[1] In the panel's words, "Patients taking other drugs whose action can intensify the sympathomimetic drug action, e.g., monoamine oxidase inhibitors, should not take nasal decongestants orally except under the advice and supervision of a physician. The Panel does not feel these restrictions should apply to topically applied nasal decongestants when administered in recommended doses because of their localized action, i.e., minimal systemic absorption." Accordingly, the panel recommended the following labeling for oral nasal decongestants: "Drug Interaction Precaution: Do not take this product if you are presently taking a prescription antihypertensive or antidepressant drug containing a monoamine oxidase inhibitor except under the advice and supervision of a physician." In 1985, the FDA issued its Tentative Final Monograph for nasal decongestants.[2] In responding to requests that the warning be clarified for consumers, FDA suggested similar labeling: "Do not take this product if you are presently taking a prescription drug for high blood pressure or depression, without first consulting your doctor." Identical labeling was also proposed for other nonprescription products containing sympathomimetic amines, such as bronchodilator products with ephedrine or epinephrine for asthma.

In 1992, the FDA became aware of an additional issue regarding MAOIs. Dextromethorphan was found to be a possible cause of a potentially deadly interaction in patients taking MAOIs.[3] Among the numerous cases reported, a 26-year-old female had been taking 15 mg of phenelzine four times daily for a month but took a 30-mg dose after she missed an earlier one. She also ingested 2 oz. of a dextromethorphan-containing cough syrup, which led to nausea, dizziness, and collapse. She was severely hypotensive when taken to the hospital, with a systolic that did not rise above 70 mmHg and a temperature of 107.6 to 107.96ºF. She died of a cardiac arrest four hours postadmission.

A 15-year-old female taking 15 mg of phenelzine three times daily for depression took eight capsules containing 15 mg of dextromethorphan, 6.25 mg of phenindamine, and 5 mg of phenylephrine, followed by another five capsules three hours later. She was found to have fixed, dilated pupils, lack of a gag reflex, mild spasticity, and hyperreflexia of the upper limbs. Resuscitation efforts were unsuccessful. Her autopsy revealed acute cerebral edema, marked acute pulmonary edema, and hemohydrothorax.

The FDA observed that prescribing of MAOIs had increased in the years preceding 1992. Thus, FDA proposed in the 1992 document to extend the MAOI warning to dextromethorphan, with wording as follows, "Do not use this product if you are taking a prescription drug containing a monoamine oxidase inhibitor (MAOI) (certain drugs for depression or psychiatric or emotional conditions), without first consulting your doctor. If you are uncertain whether your prescription drug contains an MAOI, consult a health professional before taking this product." In 1993, the FDA published the final monograph on this topic, including a discussion of the comments it had received.[4] In response to two such comments, the agency decided to include selegiline as a possible source of drug interactions, to require a reference to selegiline's use in Parkinson's disease, and to indicate that a two-week washout period should be observed. The final label required by the FDA reads: "Do not use this product if you are now taking a prescription monoamine oxidase inhibitor (MAOI) (certain drugs for depression, psychiatric or emotional conditions, or Parkinson's disease), or for 2 weeks after stopping the MAOI drug. If you are uncertain whether your prescription drug contains an MAOI, consult a health professional before taking this product." The proposed labels for nasal decongestants and bronchodilators for asthma were identical to that proposed for dextromethorphan, as well as in the final monograph that eventually appeared for bronchodilators.

The FDA Panel assigned to review anorectal products recognized in its 1980 report that topical vasoconstrictors in hemorrhoid products (e.g., phenylephrine) could be absorbed in sufficient quantities to interact with MAOIs.[5] The FDA-required label for these products is not as complete as the labels above, stating only, "Ask a doctor or pharmacist before use if you are presently taking a prescription drug for high blood pressure or depression."[6] Furthermore, the label ignores the use of selegiline for Parkinson's disease.

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