NEET MDS Lessons
Pharmacology
Carbonic anhydrase inhibitors
Acetazolamide, Dichlorphenamide, Methazolamide, Ethoxzolamide
Mechanism of Action
1. Carbonic anhydrase (CA) facilitates excretion of H+ and recovery of bicarbonate by the proximal renal tubule and ciliary epithelium of the eye. Sodium is recovered in exchange for H+.
2. Inhibitors block CA block sodium recovery. A very mild diuresis is produced (this is really a side effect of their use in glaucoma) because relatively unimportant mechanism for Na recovery and because proximal tubule site means that other sodium recovery mechansims continue to process their normal fraction of the sodium load.
Griseofulvin
- Griseofulvin is an antifungal drug. It is used both in animals and in humans, to treat ringworm infections of the skin and nails. It is derived from the mold Penicillium griseofulvum.
- It is administered orally.
Glitazones (thiazolidinediones)
Thiazolidinediones, also known as the "-glitazones"
pioglitazone
rosiglitazone
Mechanism
bind to nuclear receptors involved in transcription of genes mediating insulin sensitivity
peroxisome proliferator-activating receptors (PPARs)
↑ insulin sensitivity in peripheral tissue
↓ gluconeogenesis
↑ insulin receptor numbers
↓ triglycerides
Clinical use
type II DM
as monotherapy or in combination with other agents
contraindicated in CHF
associated with increased risk of MI (in particular rosiglitazone)
ANTIDEPRESSANTS
Monoamine uptake inhibitors
1. Tricyclic antidepressants (TCAs)
2. Selective serotonin reuptake inhibitors (SSRIs)
3. Serotonin-norepinephrine reuptake inhibitors(SNRIs)
4. Norepinephrine reuptake inhibitor
Monoamine oxidase inhibitors (MAOIs)
Monoamine receptor antagonists
PHARMACOLOGY OF VASOCONSTRICTORS
All local anesthetics currently used in dentistry today produce some degree of vasodilatation. This
characteristic results in the increased vascularity of the injected site and results in a shorter duration of local
anesthetic action due enhanced uptake of the local anesthetic into the bloodstream.
- Using a “chemical tourniquet” to prolong the effect of local anesthetics
- The vasoconstrictive action of epinephrine reduces uptake of local anesthetic resulting in a significant increase in the duration of local anesthetic action.
- the addition of vasoconstrictors in local anesthetic solutions will:
1. Prolong the effect of the local anesthetic
2. Increase the depth of anesthesia
3. Reduces the plasma concentration of the local anesthetic
4. Reduces the incidence of systemic toxicity
5. Reduces bleeding at surgical site
Local anesthetics containing epinephrine produce:
1. Localized
VASOCONSTRICTION MEDIATED BY ALPHA RECEPTOR ACTIVATION
i. Hemostasis at surgical site
ii. Ischemia of localized tissue
2. Systemic
HEART
i. Increased heart rate (β1)
ii. Increased force and rate of contraction (β 1)
iii. Increased cardiac output
iv. Increases oxygen demand
v. Dilation of coronary arteries
vi. Decreases threshold for arrhythmias
LUNGS
i. Bronchodilation (β2 )
SKELETAL MUSCLE
i. Predominately vasodilation (fight or flight response) (β 2 )
CNS
i. Minimal direct effect due to difficulty in crossing the blood-brain barrier. Most effects on the CNS are manifestations of the vasoconstrictor on other organs such as the heart.
Concentrations of vasoconstrictors
1. Epinephrine The most commonly used epinephrine dilution in dentistry today is 1:100000. However it appears that a 1:200000 concentration is comparable in effect to the 1:100000 concentration.
2. Levonordefrin Levonordefrin is a synthetic compound very similar in structure to epinephrine. It is the only alternate choice of vasoconstrictor to epinephrine. It is prepared as a 1:20000 (0.05mg/ml)(50 mcg/ml) concentration with 2 % mepivacaine.
Cardiovascular considerations
The plasma concentration of epinephrine in a patient at rest is 39 pg/ml.1 The injection of 1 cartridge of lidocaine 1:100000 epinephrine intraorally results in a doubling of the plasma concentration of epinephrine.
The administration of 15 mcg of epinephrine increased heart rate an average of 25 beats/min with some individuals experiencing an increase of 70 beats/min.
Clinical considerations
It is well documented that reduced amounts of epinephrine should be administered to patients with:
HEART DISEASE (ANGINA HISTORYOF MI)
POORLY CONTROLLED HIGH BLOOD PRESSURE
It is generally accepted that the dose of epinephrine should be limited to 0.04 mg (40 mcg) for patients that have these medical diagnoses
Anticonvulsants: include carbamazepine (use when lithium not tolerated; may not be as effective) .
valproic acid (use when lithium not tolerated; rapid onset)
Second Generation Cephalosporins
Prototype drug is CEFUROXIME (IV) and CEFUROXIME AXETIL (oral). CEFOXITIN has good activity vs. anaerobes.
1. Expanded activity against gram negative bacilli. Still have excellent activity against gram positive (Staph. and Strep.) bacteria.
Activity for Gram negative bacteria
Neisseria sp. (some gonococci resistant)
H. influenzae (including some ampicillin-resistant strains)
Moraxella catarrhalis (some resistance esp. to cefaclor)
E. coli
Proteus mirabilis
Indole + Proteus (some strains resistant)
Morganella morganii (some strains resistant)
Klebsiella pneumoniae
Serratia sp. (many strains resistant)
2. Anaerobic infections - CEFOXITIN & CEFOTETAN only
Moderate activity against Bacteroides fragilis group.
Good activity for other Bacteroides sp., Peptostreptococcus, Fusobacterium, Clostridium sp
Uses
1. Community-acquired pneumonia - Cefuroxime is widely used for empiric therapy. Has activity vs. many ampicillin-resistant H. influenzae strains.
2. Skin and soft tissue infection
3. Urinary tract infections
4. Upper respiratory tract infections (otitis media, sinusitis). Some resistance to H.influenzae to cefaclor (20-30%).
5. Mixed aerobic & anaerobic infections - Cefoxitin & Cefotetan. Resistance to B.fragilis is increasing.
6. Surgical prophylaxis - Cefoxitin or cefotetan are widely used in cases where mixed aerobic & anaerobic infections may occur, esp. intra-abdominal, colorectal, and gynecologic operations. For cardiovascular and orthopedic procedures, cefuroxime and others may be used, but cefazolin is cheaper and appears to work well.