Diagnosis Of ADRs

Diagnosis of ADRs / causality assessment of ADRs / Detection of ADRs:

•it is the cause and effect relationship between drugs and reactions. The signs and symptoms are quite similar to the signs and symptoms of other diseases.

E.g. tachycardia,  tachypnea, nausea are the side effects of some drugs but also these signs may be due to CVS or GIT disorders so the differtiation is quite difficult to detect. This detection is broader part of diagnosis.

Take history:

If they are taking any drug the ADRs might be due to this drug.

ADRs are caused by

•RX drugs

•OTC

•Herbs

•Prolonged use

Patient do not consider them drug.

E.g. OTC paracetamol chronic use increases the chances of hypertension.

•Panadol CF is sympatho mimetic may increase the blood pressure.

•Chronic use of aspirin cause the increase in blood pressure.

Herbs causing ADRs:

•gingko biloba can cause haemorrhage

•if hypertension patient taking raw garlic it can cause peptic ulcer.

•ephidra can causes tachycardia,  insomnia and hypertension .

The above signs are associated with the drug use but these signs may be very similar to other signs of diseases. The process become quite difficult if multiple drugs are used together.

First thing is to take history next is temporal relationship.* diagnosis of ADRs 

Temporal relationship:

Time relationship between use of drugs and occurrence of ADR. The cause must be precede effect.  There should be plausible relationship (logical relationship) between time and effect.

E.g. Paracetamol is taken just one dose and liver failure happens . This liver failure is nit due to the paracetamol because paracetamol cause hepatic toxicity only in dose >4000 mg/d

One day use of any drug , cancer is caused this cancer is due to this drug is not possible the cancer cause is something else.

Most drugs causes birth defects to the fetous in 1^st trimester because of organogenesis. In allergic ADRs pre exposure is necessary.

Drugs which are dose dependent ADRs usually occur after achieving steady state. Steady state are usually achieved in 4-5 doses.

The signs and symptoms may abate or disappear by decreasing the dose or withdraw the drug.* diagnosis of ADRs 

Background frequency of an event:

How much common this event is and how much this event is associated with the drug.

Suppose;

Nausea, vomiting,  headache and fatigue is very common they may not be associated with drug.

Uncommon conditions such as angioedema,  haemolytic anaemia,  anaphylaxis and agranulocytes they may be associated with drugs.* diagnosis of ADRs 

Pattern recognition of ADRs:

In majority cases we know the pharmacology of the drugs so they are easily practicable and easily determined.

E.g. amikacin causes ototoxicity this is the known ADR of amikacin.

•PPIs cause severe diarrhoea this is known ADR.

ADRs of new drugs are not well established. Sometimes the patient is initially on drug 1 and the patient is ok but when he/she start taking drug 2 ADRs happens. So this ADR is because of drug 2 or drug drug interaction.

Withdraw the drug 2 look for signs and symptoms if disappears gradually then this is drug drug interaction between drug 1 and drug 2. If present then this is because of ADR of drug 2.

The dose frequency is reduced and the therapy can be started again this is known as De challenge.

When we take digoxin with verapamil , verapamil increase the toxicity of digoxin .

How verapamil cause toxicity of digoxin?

When digoxin enter into the cell efflux pump like P-glycoprotein try to efflux digoxin out. Verapamil blocks this pump digoxin inside the cell increases and digoxin toxicity happens.* diagnosis of ADRs 

Lab investigations for ADRs:

•plasma drug concentration

•biopsy

•allergy test

They helps in establishing base line function of various organs. Providing mean for observing that what happens if the therapy is changed.

•for hepatotoxic drugs do LFTS

•for aminoglycosides do LFTS  and evaluate urea.

Naranjo scale readings for ADRs:

Naranjo scale asses causality of ADRs.

Score -4 - +13

1-4 = possible ADRs

5-8 = probable ADRs

>9 = certain ADRs

<0 = doubtful ADRs

 

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