It becomes more complicated when the plasma concentration follows a multiexponential pattern of decline and two or more half-lives can be calculated. Therefore, the time for the plasma concentration to drop from 10 to 5 mg/L is the same as from 8 to 4 mg/L or from 2 to 1 mg/L. It does not matter at what concentration half-life is measured, as long as it is measured in the mono-exponential elimination phase of the curve. For the simplest cases, elimination half-life may be used to make decisions about drug dosage, and can be derived from the plasma concentration–time profile as the time it takes for a random plasma concentration in the elimination phase to be halved (see Figure 23.7). Therefore, an increase in volume of distribution also increases elimination half-life. It is, however, the drug in plasma that is exposed to the elimination mechanisms. On the other hand, the larger the volume of distribution, the more the drug is concentrated in the tissues rather than in the plasma. This is because a decrease in the efficiency of elimination (and therefore in clearance) would, of course, cause an increase in the time needed to reduce the plasma concentration by 50 percent.

History of psychosis, presence of infection at the injection site, uncontrolled bleeding, or spinal canal obstruction that impairs CSF circulation, IV administration Drug Interactions of Concern to DentistryĮlimination half-life is increased by an increase in volume of distribution or a decrease in clearance, and vice versa. Insomnia, dry skin, constipation, arthralgia, myalgia, tremor Precautions and Contraindications Side Effects/Adverse Reactions Frequentĭizziness, nausea, somnolence, weakness, diarrhea, confusion, ataxia, headache, vomiting, gait disturbance, memory impairment, hypertonia OccasionalĪnorexia, visual disturbances, anxiety, urinary retention, speech disorder, aphasia, nystagmus, paresthesia, fever, hallucinations, nervousness, vertigo Rare May titrate to maximum of 19.2 mcg/day (0.8 mcg/hr). Indications and Dosages ▸ Pain Control Intrathecal Adults, Elderly. Excreted in urine as proteolytic degradation products. 50% bound to plasma proteins metabolized in multiple organs. Reduction of chronic pain in the body PharmacokineticsĮlimination Half-life: 4.6 hr after intrathecal administration. Therapeutic Effect: Blocks excitatory neurotransmitter release, reducing sensitivity to painful stimuli. In Mosby's Dental Drug Reference (Eleventh Edition), 2014 Drug Class:Ī synthetic peptide that selectively binds to and blocks N-type voltage-sensitive calcium channels located on afferent nerves in the spinal cord.

Half life 1 beta