What is the most common Drug-Drug interactions?

 

Drug-Drug interactions

Some common drug-drug interactions / some important drug-drug interactions:

When we give warfarin with paracetamol or aspirin

Ø  Warfarin + paracetamol / aspirin

Drug-Drug Interactions When someone is taking warfarin with paracetamol (acetaminophen) this increases the risk of bleeding because paracetamol has its own antiplatelet effect, so co administration may lead to hemorrhage.

If we are using upto 2g / day paracetamol is co administered with warfarin for 7 days the action of warfarin enhances leading to increased risk of bleeding. Study also show that even at low therapeutic dose of paracetamol interact with warfarin.

It was resulted from a research that 30% of patients who were taking warfarin with paracetamol has INR value greater than 6 which is very high value above reference value (2.5 – 3.5) . This means that patient were at greater risk of developing hemorrhage.

Similar case is with aspirin when we give warfarin with aspirin but aspirin should not be more than 100 mg / d . This will increase the bleeding.

Management of drug-drug interaction/ special care:

Should be avoided or should be taken with low doses or regularly check the INR or care should be taken to those patients who are at greater risk.

Special care should be taken for the following patients who are taking warfarin + paracetamol

Ø  NSAID gastrotropathy

Ø  Smokers

Ø  More than 65 years age

Ø  PUD (peptic ulcer disease)

This undesirable action can be minimized by switching to celecoxib.

Ø  When we give ceftriaxone with ringer lactate ( R/L ) Ceftriaxone + R/L

When given together it cause chelation (complex) and cause major cardio pulmonary effect

Management of drug-drug interaction:

There should be 48 hours gap between these drugs.

Ø  When we give statins with warfarin Statins + warfarin

When we give statins particularly atorvastatin, lovastatin with warfarin which is highly protein binding 95% and 5% is free. Statins displaces warfarin from protein binding , increases free serum warfarin concentration leading to hemorrhage.

 

Statins will displace warfarin 100% from plasma protein binding leading to free warfarin concentration in serum. Free drug is pharmacologically active , warfarin is now 100% and leads to haemorrhage.

Ø  When we give statins with gemfibrozil / niacin / fenofibrate Warfarin + gemfibrozil / niacin / fenofibrate

When we give warfarin with gemfibrozil , niacin or fenofibrate , gemfibrozil is lipid modifying agent . Statins are intended to lower LDL-C . In some cases the target LDL-C not achieved for which other cholesterol lowering drugs such as niacin or fibrates may be added with statins.

These drugs can cause fibromyalgia, muscular dystrophy , rhabdomyolysis which is characterized by severe muscular pain all over the body and the creatine kinase (CK) level is increased. Creatine kinase is a muscular damage biomarker which is released from the muscles when it breaks.

Grape fruit juice with statin also increases the risk of muscular dystrophy.

Management of drug-drug interaction:

If we are prescribing statins we have to evaluate creatine kinase (CK) after 14 days again evaluate CK value . If value is increased means muscle is damaged.

This damage is also concerned by statins isolated. Risk is increases with niacin and gemfibrozil.

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Drug-Drug interactions

Some common drug-drug interactions

Some important drug-drug interactions

Drug-drug interaction When we give warfarin with paracetamol

Drug-drug interaction When we give warfarin with aspirin

Management of drug-drug interaction

Special care for drug-drug interactions

Drug-Drug interactions

Some common drug-drug interactions

Some important drug-drug interactions

Special care should be taken for the following patients who are taking warfarin with paracetamol

Drug-drug interaction When we give ceftriaxone with ringer lactate ( R/L )

Drug-drug interaction when we give statins with warfarin

Drug-drug interaction when we give statins with gemfibrozil / niacin / fenofibrate Drug-Drug interactions

Some common drug-drug interactions

Some important drug-drug interactions