Friday, February 1, 2019

How To Learn All Of These Ridiculous Drug Interactions.

What are the most common drug interactions? What is an example of a drug drug interaction? What foods interact with medications? Can herbs interact with medications?

 How To Learn All Of These Ridiculous Drug Interactions:

How To Learn All Of These Ridiculous Drug Interactions.
How To Learn All Of These Ridiculous Drug Interactions. 

The term drug- drug interaction may be define as the alteration in pharmacokinetics or effects of a drug by the presence of another drug or when we administered one drug that effect another drug .


When we take two drugs with same time then they produce undesirable change in the body which may lead to increase in toxicity and unfortunate effects of many drugs e.g. the use of two drugs such as acetaminophen along with isoniazid can leads to higher risk of liver toxicity. 

On the other hand DDIs may also affect the therapeutic response of a drug e.g. rifampicin reduces the antimicrobial effect of clarithromycin when given together. 

When one drug increase the effect of other drug then this term is refer to as synergistic effect. When one drug cancels the effect of another drug then it is called antagonistic effect. In hospital patients there is issue of DDIs which needs more attention due to severity of disease, chronic diseases, poly pharmacy, complex therapeutic regimen, and frequent modification in therapy 

. If a patient receives two drugs and one of them increase the effect of another drug then overdosing occurs which may cause serious problem in patient and increase the risk of side effect. on the other hand when one of these drug decrease the effect of other drug then this lead to under dosing of drug which cannot produce effect. 

So it is necessary to controlled drug-drug interaction in population. Example of these drug include the use of acetaminophen with codeine increase the analgesic effect of drug or the combination of amoxicillin with clavulanic acid in order to overcome resistance of bacteria to that antibiotic [5].
A DDI can also be some time beneficial e.g. co-administration of penicillin with probenecid   inhibits the renal excretion of the antibiotic and thus prolongs its half-life in plasma. Some of the known DDIs are harmful and can lead to not only undesirable and even toxic reactions but also loss of therapeutic effect. 

These latter interactions are tougher to notice because the lack of efficiency can be described by other factors such as poor compliance. In a study show among elder out patients the risk of a sub therapeutic effect as a DDI was as common as the risk of harmful reactions. Besides these important DI may occur with other pharmacologically active drug such as alcohol and nicotine.


1.2 Classification:

Drug-drug interaction was categorized into different levels as follow:

1.2.1 On the basis of onset:

It may be divided into two sub class. Rapid:

In this type of interaction the sign and symptoms is appeared after 24 hour of drugs administration. Delayed:

In this sign and symptoms appeared after 1 week administration of drug.

1.2.2 On the basis of severity:

They are classified into 4 sub types as follow. Contraindicated:

In this type of DDI the combination of drugs is contraindicated to use. Major:

In this type of DI there is risk of death and medical intrusion is required to prevent, control or minimize serious negative result. Moderate:

In this the effect of DI can worsen patient’s state and may require change in therapy. Minor:

In this type of DI little effects are formed that do not harm therapeutic outcome and there is no need to change in therapy .

1.3 Pharmacokinetic drug-drug interation:

When one drug change the absobtion, distribution, metabolism and excretion of another drug then this is called Pk DDIs.

1.3.1 Absorbtion interation:

This mainly occure when patient take two drug or poly pharmacy and one of them effect absorbtion of drug. pH:

Drug present in the stomach may be either in ionized form or non ionized form depend upon pka value. The non-ionized form of drug easly cross cell membrance because they cannot effect by  lipid bylayer and most of drug are absorbed by passive diffusion. So increase in the absorbtion of drug may also increse its bioavailibilty.

Changing the two state i.e ionized or non ionized may be useful or not for the drug. Some drug need acidic PH while other need basic PH of intestine so any change can lead to increase or decrese absorbtion. Example the use of antacid can increase the stomach PH which inhibit absorbtion of drug such as zalsatabin absrbtion is 25% is decreased, tipranavir 25 % and amprenavir decreased up to 35%. Solubility:

Drug solubilty may be effected by when two drug given togher to form comlexation. This
Mainly occur with food substance. Example when tetracycline take along with milk a chealting agent form. Most of drugs are binding with protien when given together. Example sucralfate when teke with food .

1.3.2 Distribution interaction:

Drug is transported by binding with plasma or with tissue protien. Many drug are interect with plasma protien most common with albumin, glycoprotien and lipoprotien. The acid drug are bound with albumin while basic drug are bound with glycoprotien and lipoprotien.
 Only unbound drug is availible for passive diffusion to reach extravascular and tissue sites. When paracetamol is given by a patient which is 90% bind to plasma protien and binding site is not free for other drug so liver toxicity is cause because of delayed metabolism .

Haseen Ullah Shah

Author & Editor

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