Local anesthetics dosages

Dental or surgical procedures, childhirth Infiltration or Nerve Block Local anesthetic dosage varies with procedure, degree of anesthesia, vascularity, duration. Maximum dose 4.5 mg/kg. Do not repeat within 2 hr. 

The onset of action is fast (within 60 seconds) for the intravenous anesthetic agents and somewhat slower for inhalation and local anesthetics. The induction time for inhalation agents is a function of the equiUbrium estabUshed between the alveolar concentration relative to the inspired concentration of the gas. Onset of anesthesia can be enhanced by increasing the inspired concentration to approximately twice the desired alveolar concentration, then reducing the concentration once induction is achieved (3). The onset of local anesthetic action is influenced by the site, route, dosage (volume and concentration), and pH at the injection site. 

Hydrocortisone acetate - For intralesional, intra-articular, or soft tissue injection only. Not for IV use. Dosage range is 5 to 37.5 mg. If desired, a local anesthetic may be injected before hydrocortisone acetate or mixed in a syringe and given simultaneously. 

The treatment of poisoning by local anesthetics should begin with prevention and the selection, dosage, and technique of the administration gross errors and carelessness have caused many deaths. The previous administration of a sedative, especially of the barbituric series, diminishes the risk by suppressing the convulsions and their interference with respiration, so that animals survive one and a half to four times the ordinary fatal dose of cocaine or procaine if administered hypodermically. 

Systemic absorption of topical anesthetics can result in high blood levels by any of the following mechanisms (1) too large a dosage of the local anesthetic (2) unusually rapid absorption of the drug, as in patients with marked conjunctival hyperemia (3) unusually slow drug detoxification and (4) slow elimination of the drug. 

The use of benzyl alcohol as a local anesthetic was previously discussed. It is also used as a preservative in parenteral dosage forms. However, there is some evidence that benzyl alcohol is neurotoxic and its use is contraindicated in the United Kingdom in children under 3 years of age. ° ... 

Local anesthetics are readily absorbed and distributed. They cross the intact placenta and blood-brain barrier. Recommended maximum dosages, distribution, and elimination kinetics for three of the most commonly prescribed local anesthetics are presented in Table 1. 

Hypersensitivity to amide-type local anesthetics, Adams-Stoke syndrome, supraventricular arrhythmias, Wolf-Parkinson-White syndrome. Spinal anesthesia contraindicated in septicemia. Caution Dosage should be reduced for elderly, debilitated, acutely ill safety in children has not been established. Severe renal/hepatic disease, hypovolemia, CHF, shock, heart block, marked hypoxia, severe respiratory depression, bradycardia, incomplete heart block. Anesthetic solutions containing epinephrine should be used with caution in peripheral or hypertensive vascular disease and during or following potent general anesthesia. Sulfite sensitivity or asthma for some local and topical anesthetic preparations. Tartrazine or aspirin sensitivity with some topical preparations. Anxiety, insomnia, apprehension, blurred vision, loss of hearing acuity, and nausea CNS depression, convulsion and respiratory depression... 

Effective in the management of severe postoperative, chronic, or cancer pain. Spinal opioids can be administered by a single bolus injection into the epidural or subarachnoid space or by continuous infusion via an indwelling catheter. Dosage requirement by these routes is significantly less than with IV administration (epidural opioid doses 10-fold lower than IV doses intrathecal opioid doses 100-fold lower than IV doses). Morphine, hydromorphone, fentanyl, and sufentanil are effective when administered intrathecally. The most commonly used local anesthetic in continuous epidural infusions is bupivacaine. Fentanyl, morphine, or hydromorphone is usually combined with bupivacaine for epidural infusions. 

Use it cautiously and in rednced dosage with alcohol, barbiturates, and other sedatives, narcotics, dextromethorphan, and tricyclic antidepressants. Cocaine and vasoconstrictors in local anesthetics may precipitate a hypertensive response (see also Figure 80). 

The shrinking of mucous membranes decreases operative bleeding while improving surgical visualization. Comparable vasoconstriction can be achieved with other local anesthetics by the addition of a low concentration of a vasoconstrictor such as phenylephrine (0.005%). Epinephrine, topically applied, does not prolong the duration of action of local anesthetics applied to mucous membranes because of poor penetration. Maximal safe total dosages for topical anesthesia in a healthy 70-kg adult are 300 mg for lidocaine, 150 mg for cocaine, and 50 mg for tetracaine. 

Local anesthetic activity usually increases with increasing lipid solubility. Unfortunately, this increase in lipid solubility is often inversely related to water solubility. For this reason, a suitable parenteral dosage form may not be available for these agents because of poor water solubility under acceptable conditions. For example, benzocaine, which lacks a sufficiently basic aliphatic amino group needed for salt formation, is practically insoluble in water at a neutral pH. Protonation of the aromatic amino group in benzocaine results in a salt with a pKa of 2.78,... 

Amide-type local anesthetics (e.g., procainamide and lidocaine) also possess antiarrhythmic activity when given parenterally and at a subanesthetic dosage. Although this action can be attributed to their actions on sodium channels in cardiac tissues, current evidence suggests a distinctly different mechanism of action with respect to the modulation of channel receptors and the location of binding sites for these compounds (19,20). 

Stereochemistry of the local anesthetics, however, plays an important role in their observed toxicity and pharmacokinetic properties. For example, ropivacaine and levobupivacaine, the only optically active local anesthetics currently being marketed, have considerably lower cardiac toxicities than their close structural analogue, bupivacaine (45). Furthermore, the degree of separation between motor and sensory blockade is more apparent with ropivacaine and levobupivacaine relative to bupivacaine at a lower end of the dosage scale (46). Thus, the observed cardiac toxicity of bupivacaine has been attributed to the F -( + )-bupivacaine enantiomer (41,42,43). The exact mechanisms for this enantiomeric... 

Benzocaine (ethyl p-aminobenzoate) is used topically by itself or in combination with menthol or phenol in nonprescription dosage forms such as gels, creams, ointments, lotions, aerosols, and lozenges to relieve pain or irritation caused by such conditions as sunburn, insect bites, toothache, teething, cold sores or canker sores in or around the mouth, and fever blisters. Benzocaine is a lipophilic local anesthetic agent with a short duration of action. 

Local anesthetics are able to depress or block nerve conduction at low dosage Davis has demonstrated a relationship between antiarrhythmic potency, local anesthesia and neuromuscular transmission . The actions of antiarrhythmic agents to slow conduction can be explained by their depression of neuromuscular transmission. Slowed conduction can be explained through a retardation of the nerve impulse propagation, by increasing the electrical excitation threshold and reducing the rate of rise of the action potential . ... 

Further studies have shown that decreased intracellular K" concentration was required before ouabain induced arrhythmias in dogs. Increased Na was not necessary. Local anesthetic agents such as quinidine, butidrine and procaine amide reduced K loss through a membrane stabilization effect of red blood cells and not by a direct interaction with ATPase ". Andersen demonstrated that lidocalne was able to alter membrane permeability to Na and at therapeutic dosage. Toxic dosage levels caused a major disruption of membrane integrity which resulted in diffusion of Na and K . The cationic form appeared to be the active species of the drug in human red blood cells. 

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