DRUG ALERT: AVOID THESE DRUG INTERACTIONS...Part 2

Watch out for the following drug to drug and drug to food interactions in this DRUG ALERT SERIES:


Non steroidal Anti inflammatory Drugs (NSAIDS) and Anti-hypertensive Drugs

Non steroidal anti inflammatory drugs (NSAIDs) are drugs often used for pains with an inflammatory component (a common sign of inflammation is swelling). Some of them are also useful in calming a fever (anti pyretic action). Popular examples of NSAIDs include:

• Paracetamol
• Aspirin
• Ibuprofen
• Diclofenac
• Naproxen
• Piroxicam
• Indomethacin

They are used in common painful conditions such as toothache, muscular aches and pains, arthritic pain, pain due to sprain and strain, menstrual pains and fever relief.

Anti hypertensive drugs are used in treating and controlling high blood pressure. Anti hypertensive drugs are grouped into different classes based on the way they act to produce high blood pressure control. The various classes of anti hypertensive drugs include:

• Thiazide diuretics e.g hydrochlorthiazide
• Potassium sparing diuretic e.g Amiloride
• Loop diuretics e.g frusemide
• Angiotensin converting enzyme (ACE) inhibitors e.g Lisinopril
• Angiotensin receptor blockers (ARB) e.g Losartan
• Beta Blockers with only Beta-1 receptor selectivity e.g Atenolol
• Beta Blockers with Alpha-1 receptor antagonist activity e.g  labetalol
• Beta Blockers with intrinsic sympathomimetic activity e.g Acebutolol
• Vasodilators e.g Hydralazine
• Calcium Channel Blockers e.g Amlodipine
• Aldosterone Antagonists (Selective) e.g Spirinolactone
• Alpha-2 agonist, Centrally acting e.g Methyldopa
• Renin Inhibitors e.g Aliskiren
• Alpha Blockers e.g Doxazosin
• Reserpine e.g Reserpine

Choice of what class of anti hypertensive drug is prescribed to best treat a hypertensive person is dependent on a variable of clinical factors as interpreted by the healthcare giver.

It is common occurrence for a hypertensive person already on anti-hypertensive medication to need NSAIDs so as to bring relief to inflammatory pain that do occur without warning every now and then such as in toothaches, general body pain, muscular sprains and arthritic pain (Very common in older people with hypertension).

But is it safe to use NSAIDs with just any class of Anti-hypertensive drugs whenever the need do arise?


DRUG ALERT: THERAPEUTIC FAILURE WITH KIDNEY TOXICITY

If you are on an anti-hypertensive medication and you need to use NSAIDs for inflammatory pain, watch out for these drug to drug interactions:

(1) All types of NSAIDs (e.g aspirin), when used together with any diuretic class of anti-hypertensives (e.g hydrochlorothiazide) and Angiotensin Converting enzyme inhibitor class (e.g lisinopril) or Angiotensin Receptor Blocker class of anti hypertensives (e.g losartan) reduces their anti hypertensive action which could lead to anti hypertensive treatment failure. There is also the significant risk of kidney toxicity associated with the use of these three classes of drugs together.

(2) Naproxen, a potent NSAID for inflammatory relief, when used at a dose of 500mg twice daily for two weeks together with ramipril (an ACE inhibitor class of anti hypertensive medication) or valsartan (an ARB class of anti-hypertensive medication) significantly reduces the potency of these anti-hypertensives to a point requiring upward dosage adjustment for these anti hypertensives. There is also increased risk of kidney toxicity.

(3) Paracetamol, as part of a surprise finding in a study was seen to blunt and reduce the anti hypertensive action of ramipril, valsartan and aliskiren. There is evidence to show that if paracetamol is giving together with any of these three drugs, paracetamol is capable of increasing blood pressure to some degree.


Artemisinin Based Combination Therapy (ACT) For Malaria and Vitamin C

Artemisinin based combination therapy is the gold standard in malaria treatment today. It is a globally acknowledge standard reputed to be very potent against multi-resistant strains of Plasmodium Falciparum, the organism responsible for malaria.

Artemisinin based combination anti malaria drugs are a combination of any one of the artemisinin based derivates such as:

• dihydroartemisin
• artesunate
• arthemeter
• arteether

along with another class of an equally powerful anti malaria agent that shows good stability, improved synergistic actions and high margin of safety when combined with artemisinin based derivatives. Examples of such classes of anti-malarials include:

• Quinoline-methanols e.g Mefloquine
• 4-amino-quinolenes e.g Amodiaquin
• Bisquinolines e.g Piperaquine
• Sulphone-pyrimethamine combination e.g Sulphametopyrazine-Pyrimethamin
• Phenantrine anti-malarials e.g lumefantrin

Vitamin C's (also known as ascorbic) is a water soluble vitamin needed for normal growth and body development. Vitamin C is a powerful antioxidant useful in wound healing, repair and maintenance of cartilage, bone and teeth. It also aids absorption of iron and is very important in boosting the function of the immune system.

For people with malaria infection, it is common practice to administer Artemisinin based combination anti-malarial's (ACT's)with vitamin C.

Are there any risks?


DRUG ALERT: ANTI-MALARIA TREATMENT FAILURE

Vitamin C when co-administered with anti-malarial drugs, particularly ACT's, diminishes their antimalarial action. Recent studies show that Vitamin C renders ACT's less effective when co-admistered together. A study conducted in Nigeria involving 80 malaria infected adult patients (OC Adamanya et al.,Int Pure Appl Sci Technol, 2012, 10, 5157) showed that administration of orange juice, grapefruit juice or vitamin C concomitantly with artesunate and amodiaquine severely diminishes the efficacy and potency of these antimalarial drugs. In this study, for most patients under concomitant adiministration of Vitamin C with ACT's, the malaria parasite was not cleared from the blood at the end of treatment regimen unlike when such antimalarial drugs where administered without vitamin C.

Vitamin C may also increase malaria parasitaemia as the uptake of ascorbic acid into red blood cells is increased during malaria infection. Vitamin C particular enhances the development of young malaria parasites as it appears Plasmodium Falciparum (The organism causing malaria) does need vitamin C for development.


Reference: 

(1) Gualtierotti R, Zoppi A, Mugellini A, Derosa G, DÁngelo A, Fogari. Effect of Naproxen and acetaminophen on blood pressure lowering by ramipril, valsartan and aliskiren in hypertensive patients. Expert Opin Pharmacotherapy. 2013; 14:1875-1884.

(2) R Stocker et al., Biochim  Phyys Acta 1986, 881, 391-7

(3) E Marva et al., Trop J Med Parasitol 1992, 43, 17-23

(4) CR Brockelman et.al, Parasitol Res 1987 73, 107-12.