📖 Pharmacology
Effects and Toxic Actions on Organ Systems
PharmacologyEffects and Toxic Actions on Organ Systems
1. Local anesthetics (dose dependent) interfere with transmission in any excitable tissue (e.g. CNS and CVS).
2. CNS effects
a. Central neurons very sensitive.
b. Excitatory-dizziness, visual and auditory disturbances, apprehension, disorientation and muscle twitching more common with ester type agents.
c. Depression manifested as slurred speech, drowsiness and unconsciousness more common with amide type agents (e.g. lidocaine).
d. Higher concentrations of local anesthetic may eventually produce tonic-clonic[grand mal] convulsions.
e. Very large doses may produce respiratory depression which can be fatal. Artificial respiration may be life-saving.
3.CVS effects
a. Local anesthetics have direct action on the myocardium and peripheral vasculature by closing the sodium channel, thereby limiting the inward flux of sodium ions.
b. Myocardium usually depressed both in rate and force of contraction. Depression of ectopic pacemakers useful in treating cardiac arrhythmias.
c. Concentrations employed clinically usually cause vasodilation in area of injection.
d. Vasoconstrictors such as epinephrine may counteract these effects on myocardium and vasculature.
4. Local Tissue Responses
a. Occasionally focal necrosis in skeletal muscle at injection site, decreased cell motility and delayed wound healing.
b. Tissue hypoxia may be produced by action of excessive amounts of vasoconstrictors.
Epilepsy
Pharmacology
Epilepsy
- Abnormal synchronous APs of groups of neurons in various parts of brain
- Many casues (infection, fever, tumors, injury, lyte imbalance, etc)
- Therapy aimed to reduce excitability of neurons
1.Increasing GABA
Benzodiazepines (Clonazepam, Diazepam) - Diazepam used for status epilepticus
Barbiturates (Phenobarbital)- Benzos and Barbituates increase GABA channel - hyperpolarization of neurons
Gabapentin - Increases gaba release
Valproic acid - Increases GABA, also blocks Na+ and Ca2+ channels, and increase K+ conductance
2.Alter transmembrane flow of ions
Phenytoin- Blocks Na+ channels
Carbamazepine - Blocks Na+ channels and potentiates postsynaptic effect of GABA
Ethosuximde - Blocks Ca2+ channels
Iamotrigine - Blocks Na+ channels
3. Decrease glutamate excitatory tone
Glutamate antagonists have too many side effects and none are on the market as anticonvulstants yet
Antiplatelet Drugs
PharmacologyAntiplatelet Drugs:
Whereas the anticoagulant drugs such as Warfarin and Heparin suppress the synthesis or activity of the clotting factors and are used to control venous thromboembolic disorders, the antithrombotic drugs suppress platelet function and are used primarily for arterial thrombotic disease. Platelet plugs form the bulk of arterial thrombi.
Acetylsalicylic acid (Aspirin)
• Inhibits release of ADP by platelets and their aggregation by acetylating the enzymes (cyclooxygenases or COX) of the platelet that synthesize the precursors of Thromboxane A2 that is a labile inducer of platelet aggregation and a potent vasoconstrictor.
• Low dose (160-320 mg) may be more effective in inhibiting Thromboxane A2 than PGI2 which has the opposite effect and is synthesized by the endothelium.
• The effect of aspirin is irreversible.
Chloral hydrate
PharmacologyChloral hydrate
1. Short-acting sleep inducer—less risk of “hangover” effect the next day.
2. Little change on REM sleep.
3. Metabolized to trichloroethanol, an active metabolite; further metabolism inactivates the drug.
4. Used for conscious sedation in dentistry.
5. Can result in serious toxicity if the dose is not controlled.