What is high therapeutic index?

The larger the therapeutic index (TI), the safer the drug is. If the TI is small (the difference between the two concentrations is very small), the drug must be dosed carefully and the person receiving the drug should be monitored closely for any signs of drug toxicity. Related Term(s)

What happens if therapeutic index is high?

A higher therapeutic index is preferable to a lower one: a patient would have to take a much higher dose of such a drug to reach the toxic threshold than the dose taken to elicit the therapeutic effect.

When a drug has a low therapeutic index?

1-3 Therefore, preventing DRPs would benefit both patients and society. Drugs with a narrow therapeutic index (NTI-drugs) are drugs with small differences between their therapeutic and toxic doses, implying that small changes in dosage or interactions with other drugs could cause adverse effects.

What does a high therapeutic window mean?

Definition: The dose range of a drug that provides safe and effective therapy with minimal adverse effects. Generally, at low concentrations, a drug runs the risk of being ineffective; at high concentrations, the risk of adverse effects is increased.

What is safe therapeutic index?

therapeutic index, margin of safety that exists between the dose of a drug that produces the desired effect and the dose that produces unwanted and possibly dangerous side effects.

What does it mean when a drug is in therapeutic range?

The therapeutic range of a drug is the dosage range or blood plasma or serum concentration usually expected to achieve the desired therapeutic effect. This does not mean that patients may not achieve benefit at concentrations below the minimum threshold, or may not experience adverse effects if kept within the range.

How do you interpret therapeutic index?


  1. therapeutic index of a drug is the ratio of the dose that produces toxicity to the dose that produces a clinically desired or effective response.
  2. TD50 = the dose of drug that causes a toxic response in 50% of the population.
  3. ED50 = the dose of drug that is therapeutically effective in 50% of the population.

Which antibiotic has a high therapeutic index?

Most antibiotics, such as the β-lactams, macrolides and quinolones have a wide therapeutic index and therefore do not require therapeutic drug monitoring. Some, such as the aminoglycosides and vancomycin, have a narrow therapeutic index, and toxicity may be severe and irreversible.

Why is the therapeutic index important?

The therapeutic index (TI) — which is typically considered as the ratio of the highest exposure to the drug that results in no toxicity to the exposure that produces the desired efficacy — is an important parameter in efforts to achieve this balance.

Does aspirin have a narrow therapeutic index?

Clearly, most clinicians do not consider aspirin a Narrow Therapeutic Index drug. However, in its use as an antirheumatic drug, the dose required to achieve the therapeutic effects is close to the dose that results in undesirable toxicity.

What is the therapeutic index of paracetamol?

There have been no reports of acute toxicity in healthy adults ingesting a single dose of paracetamol below 125 mg/kg; historical data suggest that toxicity gen- erally occurs only above 150 mg/kg (176) (the therapeutic paracetamol dose is 10–15 mg/kg, therefore the therapeutic index is ~10).

How do you find therapeutic index?

The therapeutic index formula T 1 = 3 W a × 10 – 4 was derived from T1 = LD50/ED50 and ED50 = L D 50 3 x W a × 10 – 4 . Findings have shown that, therapeutic index is a function of death reversal (s), safety factor (104) and weight of animal (Wa).

Does digoxin have a high therapeutic index?

Digoxin has a narrow therapeutic index [1, 23, 25] so small variations in plasma concentration may readily result in toxic or sub therapeutic concentrations. Thus, consistency in bioavailability is important. Moreover, toxic symptoms can be evident with normal digoxin concentrations [25].

What is a normal digoxin level?

Therapeutic levels of digoxin are 0.8-2.0 ng/mL. The toxic level is >2.4 ng/mL.

What happens if digoxin levels are too high?

Digoxin toxicity can emerge during long-term therapy as well as after an overdose. It can occur even when the serum digoxin concentration is within the therapeutic range. Toxicity causes anorexia, nausea, vomiting and neurological symptoms. It can also trigger fatal arrhythmias.

What is the therapeutic index of warfarin?

Background. Time in therapeutic range (TTR) of international normalized ratio (INR) of 2.0 to 3.0 is important for the safety and effectiveness of warfarin anticoagulation. There are few data on TTR among patients with atrial fibrillation (AF) in community-based clinical practice.

What is the therapeutic range for INR?

An INR range of 2.0 to 3.0 is generally an effective therapeutic range for people taking warfarin for disorders such as atrial fibrillation or a blood clot in the leg or lung. In certain situations, such as having a mechanical heart valve, you might need a slightly higher INR.

Does warfarin have a high therapeutic index?

Warfarin is a narrow therapeutic index drug where individual daily dose requirements vary by at least 40-fold. Inability to maintain an INR between 2 and 3 can predispose to either thrombosis (INR<2) or haemorrhage (INR>3). Warfarin is metabolised by various P450 enzymes, the most important being CYP2C9.

What INR level is vitamin K?

A 1.0-mg vitamin K dose is likely most appropriate for patients with INR values between 4.5 and 10. The fear of over-correction of the INR has limited the widespread use of vitamin K; however, our review suggests that this occurs infrequently when small doses are administered orally.

What causes high INR?

A high INR level can happen when you take warfarin (Coumadin). Warfarin helps prevent blood clots. To do this, it slows the amount of time it takes for your blood to clot. This raises your INR level.

What is the treatment for high INR?

INRs in the 5.0 to 9.0 range can be handled by holding warfarin for two days with or without a small dose of oral vitamin K in high-risk patients. Most asymptomatic, over-anticoagulated patients can be treated as outpatients in the absence of bleeding or high-risk criteria.

What happens if the INR is too high?

If the INR is too high, you are at increased risk of bleeding. But the INR will usually come back down into the right range when you skip a couple doses of your medication. If you develop bleeding while your INR is too high, it can be life-threatening.

What does an INR of 1.5 mean?

A result of 1.0, up to 1.5, is therefore normal. A low INR result means your blood is ‘not thin enough’ or coagulates too easily and puts you at risk of developing a blood clot. A high INR result means your blood coagulates too slowly and you risk bleeding.

What are the symptoms of high INR?

Signs of bleeding or a high INR are:

Gums bleed when you brush your teeth. Coughing up blood. Vomit that looks like coffee grounds. Bruising in unusual areas or for unknown reasons.

What is a critical INR level?

Normal and Critical Findings

[8]For patients who are on anticoagulant therapy, the therapeutic INR ranges between 2.0 to 3.0. INR levels above 4.9 are considered critical values and increase the risk of bleeding.

Does sugar affect INR?

No significant difference in the relationship between INR level and fasting glucose was shown by Pearson test (r = 0.070, P = 0.184).

Is INR 4.5 high?

INR 4.5-7.9

Warfarin should be restarted, if necessary, when the INR falls below 5.0. Consideration of individual clinical parameters (eg, fall risk, blood pressure, comorbidities) and the patient’s innate sensitivity to warfarin are important when deciding when treatment should be restarted.