ALERT ON DRUG INTERACTION: Iron (Ferrous salts) vs Methyldopa (Aldomet® Dopatab®)

Drug interactions occur in everyday prescriptions at health facilities and they form one of the consequences of polypharmacy, pharmacotherapy of geriatrics (old people), presence of kidney or liver dysfunction and use of drugs with narrow therapeutic index. 

This is where the pharmacists display the application of their mastery of drug related information.

Iron (Ferrous) forms one of the common medications administered to in-patients (especially pre- and post-natal) and out-patients. Pregnant women and people who have low Packed cell volume (PCV) are usually placed on blood building supplements which contain iron.
Methyldopa is an antihypertensive belonging to the class known as Centrally acting sympathoplegics. This drug works by reducing peripheral vascular resistance with a variable reduction in Cardiac output and Heart rate. It is now commonly used to manage hypertension in pregnant women.
From the foregoing, the possibility of methyldopa featuring in a prescription along sife Ferrous salts is high and interestingly, this is the case in many doctors’ prescriptions.

THE ROLE OF THE PHARMACIST: The pharmacist in his mandate of delivering pharmaceutical care to patients is responsible for contacting the prescriber to ascertain if the concormitant use of both drugs is essential to the health of the patient and to advise that if it is, that the METHYLDOPA be administered 3hours before or after intake of Iron.

REASON: Iron readily binds chemically with a lot of medicines (methyldopa) to form complexes that are poorly absorbed by the body hence when both drugs are taken at the same time, the absorption of Methyldopa is hampered and blood pressure control is not optimally achieved.

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Also, some research studies have shown that the concormitant use of IRON and METHYLDOPA will worsen hypertension in those taking the drugs and that when Ferrous was discontinued, normal Blood pressure control was achieved.
Iron is known to interact with many other medications and prevent their absorption because of its chelating ability. Some of these include levodopa/carbidopa (for treatment of parkinsonism), penicillamine (used as 2nd line agent in the treatmeant of rheumatoid arthritis), tetracycline antibiotics (doxycycline, minocycline) fluoroquinolones (ciprofloxacin, levofloxacin), Levothyroxine, etc.
It is therefore important that patients and pharmacists know this because of the menace in our society of irrational drug use among out-patients and the prevalence on medicine shops run by non-professionals. Avoiding these interactions will lead to achieving therapeutic benefits of medications, value for money spent on medicine purchase, improved health as well as reduced toxicity.

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REFERENCES
Norman R.C. Campbell & Brian B. Hasinoff (1991). Iron supplements: a common cause of drug interactions. British Journal of Clinical Pharmacology. 31:251-255.
UNIVERSITY OF MARYLAND, BALTIMORE WASHINGTON MEDICAL CENTRE: http://m.mybwmc.orgcopy, click and tweet { MTN: 2701977906270508}