Debunking the Myth of Sulfa Drugs and the Administration of Morphine

 ~Nothing in all the world is more dangerous than sincere ignorance and conscientious stupidity

 ~Martin Luther King Jr.

In today’s society of Emergency Medical care, it is very common to treat patients that have an allergy to sulfa drugs.  Most ambulance in the 21^st century carries several different types of drugs to treat patient’s medical problems or pain, whether acute or chronic. One of those many drugs that are carried is Morphine Sulfate. Morphine is a wonderful analgesic pain medication that provides pain relief which will usually last 4-5 hours with a mean of 2 hours for most patients. With morphine being an opioid analgesic it is a great resource for patients with pain. What is commonly accepted among prehospital care providers in this day and age is that we ask what kind of allergies a patient has before we administer a medication. This is a great practice; however what can happen is if we don’t understand our pharmacologic interventions, we are not providing the most adequate care for patients. The reason behind this philosophy is the common misconception that morphine sulfate is contraindicated in patients with a sulfa allergies. In this article we will discuss the difference of sulfonamides and sulfates, the implications of what medications can be given based on that a person is sensitivity to a sulfonamide, and the medications that should be withheld due to sulfonamide sensitivity.

To begin, let’s first understand what a sulfa drug is. Sulfa is short for sulfonamide. According to Britannica online encyclopedia Sulfonamide, also spelled Sulphonamide is any member of a class of chemical compounds, the amides of sulfonic acids. The class includes several groups of drugs used in the treatment of bacterial infections, diabetes mellitus, edema, hypertension, and gout. (britanica.com, definition of sulfonamide, 2016).

 A sulfonamide drug is synthetic antimicrobial agents. Sulphonamides (sulfa drugs) are one of a group of drugs that prevents the growth of bacteria. Without going into all the chemical formation of Sulphonamides, the basis is they are important in the formation of folic acid that is required by the bacteria. Folic acid is required for the synthesis of precursors of DNA and RNA both in bacteria and in mammals. Mammals obtain their folic acid in their diet but bacteria need to synthesize it. Sulphonamides inhibit the growth of bacteria but do not kill them. Many sulphonamides are rapidly excreted and very soluble in urine so they are used to treat infections of the urinary tract. That’s why we see patients who do not have hypersensitivity to sulfa, treated with a drug called Bactrim for urinary tract

Morphine Sulfate is a very common narcotic drug that is seen in the prehospital environment. Morphine is an opium derivative3, opioid analgesic that is a descending CNS depressant. (Intravenous Medications 31^st edition, pg840, copyright 2015).

 Let’s discuss salt forms of drugs first to better understand why there is a difference between a Sulfate drug and a Sulfonamide.as we know drugs are created to be absorbed into the body to have an effect. Well most of these drugs are usually a weak form of an acid or base to being with. In this form, the drug is not always optimal for dissolution or absorption into your body. A drug needs to be absorbed to have a therapeutic effect, and it usually needs to be water-soluble. Therefore, drugs are often chemically made into their salt forms to enhance how the drug dissolves and to boost its absorption into your bloodstream. Over 50% of all drug molecules used in medicine exist as salts, most frequently as hydrochloride, sodium, or sulfate salts.(Drugs.com, Clearing Up the Confusion: Drug Names and Their Salts, Sep 28, 2015)

One example of morphine presenting in two different salt forms is morphine sulfate and morphine diacetate. By just changing the salt that is chemically paired to morphine, we change morphine sulfate which is a legal Schedule II controlled substance to morphine diacetate (heroin) which is a scheduled I controlled substance. By understanding this we see that the salt formation of a medication has more to do with how the medication is absorbed into the blood stream. How soluble a medications salt is depends on how quickly the medication is absorbed into your body’s vasculature.

So the question is asked, “Does the salt form add any therapeutic effect to the drug, in addition to the main active ingredient?” It depends. Usually, the salt form of a drug does not lend therapeutic qualities to the active ingredient. Its primary purpose is to enhance pharmaceutical characteristics like dissolution, absorption, and onset of action. Different salt forms may not be bioequivalent, meaning that the therapeutic effect in the body is not expected to be the same. On the other hand, some drugs may have qualities where the salt lends a therapeutic effect. (Drugs.com, Clearing Up the Confusion: Drug Names and Their Salts, Sep 28, 2015)

Now that we have muddied the waters a little bit, let’s get back to the main question at hand, is morphine sulfate able to be given to a patient that has a hypersentivity to sulfonamides (sulfa). The answer is a resounding yes. But if by some reason you are still disbelieving the idea that we cannot give morphine because the  word sulfa is in sulfate, than by that definition we should withhold albuterol  and atropine from a patient who is allergic to sulfa because it’s full name is albuterol sulfate and atropine sulfate.

The idea of withholding morphine sulfate from a patient who is allergic or nonetheless sensitive to the drug Sulfa is a myth. A Sulfa sensitivity is sensitivity to a certain class of antibiotics. As shown above Sulfa is short for sulfonamide.  On the other hand, sulfate is a salt that is added chemically to a drug to make it easier to absorb into the body.  There is no correlation between the salt and the antibiotic. So when providing patients with Narcotic Analgesics for their acute or chronic pain condition, we no longer have to under the impression that we have to withhold morphine sulfate because the patient is allergic to Sulfonamides(sulfa).

Now there is a medication that most EMS ALS units do carry. Furosemide (Lasix) is carried for Edema associated with CHF, cirrhosis of the liver with ascites, and renal disease including the nephrotic syndrome. (Intravenous Medications 31st edition, p587, copyright 2015). The actions of Lasix is that it is a potent loop diuretic, that means it directly inhibits the reabsorption of sodium and chloride in the proximal and distal tubules and in the Loop of Henle causing increased excretion of water, sodium, chloride, magnesium, and calcium. (Intravenous Medications 31st edition, p587, copyright 2015) It is structurally related to sulfonamides. (Intravenous Medications 31st edition, p587, copyright 2015). So with this information do be cautious with administering furosemide (Lasix) to patients with a Sulfonamide (sulfa) sensitivity. (Intravenous Medications 31st edition, p587, copyright 2015)

Hopefully I have shown you the major difference between a sulfa allergy or sensitivity and the scheduled class II controlled substance morphine sulfate. We no longer have to withhold pain meds from that back pain patient with a sulfa allergy. Now go save the world with your new arsenal of narcotic analgesic medications.