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Related Concept Videos

Rational Dosage Regimen: Maintenance Dose and Loading Dose01:24

Rational Dosage Regimen: Maintenance Dose and Loading Dose

A rational dosage regimen considers a drug's pharmacokinetics, including its absorption, distribution, metabolism, and elimination from the body. By understanding these factors, the appropriate dosage can be determined, and the dosing schedule can be designed to achieve and maintain the desired therapeutic effect while minimizing adverse effects.
In most cases, drugs are administered repetitively or infused continuously to maintain a steady-state concentration in the body. At a steady state,...
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Fixed-dose regimens are a common approach to administer drugs to achieve and maintain desired levels of the drug in the body. In this dosing strategy, a specific amount of medication is given at regular intervals, often multiple times a day, to ensure a consistent drug concentration in the bloodstream.
Fixed-dose regimens can be used for various routes of administration, including intravenous (IV) injections and oral medications. For IV administration, a predetermined amount of the drug is...
Anticoagulant Drugs: Vitamin K Antagonists and Direct Oral Anticoagulants01:18

Anticoagulant Drugs: Vitamin K Antagonists and Direct Oral Anticoagulants

Oral anticoagulants are vital tools in preventing and treating blood clotting disorders. This diverse class of medications can be categorized as vitamin K antagonists, exemplified by warfarin, and direct thrombin inhibitors (DTIs), such as dabigatran, as well as factor Xa inhibitors, including rivaroxaban.
Warfarin, a prominent vitamin K antagonist family member, exerts its effect by inhibiting the enzyme VKORC1 (vitamin K epoxide reductase complex 1). By hindering this enzyme, warfarin...
Renal Failure: Dose Adjustments01:11

Renal Failure: Dose Adjustments

In patients with renal impairment, drugs undergo significant changes in their pharmacokinetics, which require dosage adjustments to ensure safe and effective therapy.
Reduced renal clearance and elimination rate are common outcomes of renal impairment. These alterations lead to a prolonged elimination half-life and an altered apparent volume of distribution for drugs. As a result, dosage adjustments are typically necessary to maintain optimal drug levels in the body.
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Dosage Regimens: Partial Pharmacokinetic Parameters01:01

Dosage Regimens: Partial Pharmacokinetic Parameters

It is not uncommon for complete drug pharmacokinetic profiles to remain elusive in pharmacokinetics. This necessitates certain educated assumptions by pharmacokineticists to determine appropriate dosage regimens without comprehensive pharmacokinetic data from animal or human studies. One prevalent assumption is setting the bioavailability factor, denoted as F, to 1 or 100%. This assumption caters to the scenario where a drug doesn't achieve full systemic absorption, resulting in the patient...
Drug Dosing: Geriatric Patients01:15

Drug Dosing: Geriatric Patients

Elderly individuals encompass a diverse population with varying degrees of age-related physiological changes. Defining the elderly presents challenges, as the geriatric population is often arbitrarily categorized as individuals older than 65. However, many individuals in this group lead active and healthy lives, with an increasing number surpassing 85 years and falling into the older elderly category. Physiological changes associated with aging impact performance capacity and homeostatic...

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The WATCHMAN Left Atrial Appendage Closure Device for Atrial Fibrillation
23:33

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Published on: February 28, 2012

Warfarin maintenance dosages in the very elderly.

Dana L Singla1, Gregory B Morrill

  • 1College of Pharmacy, Midwestern University, Glendale, AZ, USA. dsingl@midwestern.edu

American Journal of Health-System Pharmacy : AJHP : Official Journal of the American Society of Health-System Pharmacists
|May 20, 2005
PubMed
Summary

Elderly patients require lower warfarin maintenance dosages as they age. This study found that older individuals, particularly those over 75, needed significantly less warfarin to maintain a stable International Normalized Ratio (INR).

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Area of Science:

  • Geriatric Medicine
  • Pharmacology
  • Clinical Pharmacy

Background:

  • Warfarin is a common anticoagulant medication.
  • Dosage adjustments are often necessary based on patient factors, including age.
  • Understanding age-related dosage requirements is crucial for safe and effective anticoagulation therapy.

Purpose of the Study:

  • To investigate the relationship between age and warfarin maintenance dosage in elderly patients.
  • To determine if increasing age correlates with a need for lower warfarin doses in patients with a stable International Normalized Ratio (INR).

Main Methods:

  • Retrospective review of patient records from an anticoagulation clinic (October 2000 - July 2002).
  • Inclusion criteria: age >50 years, targeted INR of 2-3, two consecutive INRs within range.
  • Patients categorized into age groups: <75, 75-79, 80-84, and ≥85 years.

Main Results:

  • 253 out of 532 reviewed charts met inclusion criteria.
  • Mean patient age was 80.6 years.
  • A significant inverse relationship was observed between age and mean daily warfarin dose; patients ≥85 years received 3.5 mg/day compared to 4.9 mg/day for those <75 years.

Conclusions:

  • Warfarin maintenance dosage in elderly patients is inversely related to age.
  • This effect is particularly pronounced in patients over 75 years.
  • Age is a critical factor in determining appropriate warfarin dosing for elderly individuals.