Hypothalamic - Pituitary Drugs

Somatropin

Growth hormone (GH) mimetic

Mechanism

agonist at GH receptors
increases production of insulin growth factor-1 (IGF-1)

Clinical use

GH deficiency
increase adult height for children with conditions associated with short stature 
Turner syndrome
wasting in HIV infection
short bowel syndrome

Toxicity

scoliosis
edema
gynecomastia
increased CYP450 activity

Octreotide

Somatostatin mimetic

Mechanism

agonist at somatostatin receptors

Clinical use

acromegaly
carcinoid
gastrinoma
glucagonoma
acute esophageal variceal bleed

Toxicity

GI upset
gallstones
bradycardia
Oxytocin

Mechanism

agonist at oxytocin receptor

Clinical use

stimulation of labor
uterine contractions
control of uterine hemorrhage after delivery
stimulate milk letdown

Toxicity

fetal distress 
abruptio placentae 
uterine rupture
Desmopressin
ADH (vasopressin) mimetic

Mechanism

agonist at vasopressin V2 receptors

Clinical use

central (pituitary) diabetes insipidus
hemophilia A (factor VIII deficiency)
increases availability of factor VIII
von Willebrand disease
increases release of von Willebrand factor from endothelial cells

Toxicity

GI upset
headache
hyponatremia
allergic reaction

Patient positioning

The most common medical emergency encountered in the dental office setting is syncope. So patients in the supine or semi-supine position to improve venous return and cerebral blood flow provided that the position is tolerated by the patient and is appropriate for their medical condition.

Examples of calculations of doses of vasoconstrictors

Ratio concentrations represent grams per millilitre

1:100,000 = 0.01 mg/mL or 10 µg/mL

1:200,000 = 0.005 mg/mL or 5 µg/mL

1:50,000 = 0.02 mg/mL or 20 µg/mL

1 cartridge of epinephrine 1:200,000 = 9 µg

1 cartridge of epinephrine 1:100,000 = 18 µg

1 cartridge of epinephrine 1:50,000 = 36 µg

1 cartridge of levonordefrin 1:20,000 = 90 µg

Routes of Drug Administration

Intravenous

• No barriers to absorption since drug is put directly into the blood.
• There is a very rapid onset for drugs administered intravenously.  This can be advantagous in emergency situations, but can also be very dangerous.
• This route offers a great deal of control in respect to drug levels in the blood.
• Irritant drugs can be administer by the IV route without risking tissue injury.
• IV drug administration is expensive, inconvenient and more difficult than administration by other routes.
• Other disadvantages include the risk of fluid overload, infection, and embolism.  Some drug formulations are completely unsafe for use intravenously.

Intramuscular:

• Only the capillary wall separates the drug from the blood, so there is not a significant barrier to the drug's absorption.
• The rate of absorption varies with the drug's solubility and the blood flow at the site of injection.
• The IM route is uncomfortable and inconvenient for the patient, and if administered improperly, can lead to tissue or nerve damage.

Subcutaneous

Same characteristics as the IM route.

Oral

• Two barriers to cross: epithelial cells and capillary wall.  To cross the epithelium, drugs have to pass through the cells.

• Highly variable drug absorption influenced by many factors:  pH, drug solubility and stability, food intake, other drugs, etc.
• Easy, convenient, and inexpensive.  Safer than parenteral injection, so that oral administration is generally the preferred route.
• Some drugs would be inactivated by this route
• Inappropriate route for some patients.
• May have some GI discomfort, nausea and vomiting.
• Types of oral meds = tablets, enteric-coated, sustained-release, etc.
• Topical, Inhalational agents, Suppositories

Propofol -Intravenous Anesthetics

- A nonbarbiturate anesthetic
- It is very lipid-soluble, acts rapidly and has a short recovery time.
- It is associated with less nausea and vomiting than some of the other IV anesthetics.
- Propofol is very similar to thiopental in its effects on the cardiorespiratory system.
- It does not have any analgesic properties but lowers the dose of opioid needed when the two agents are used in combination.

- The most significant adverse cardiovascular effect associated with propofol administration is hypotension. It should be used with caution in patients with cardiac disease.

Local anesthetic selection

Local anesthetics are typically divided into 3 main categories:

short, intermediate and long acting local anesthetics.

Based on duration of the procedure and the duration of the individual agents

Short acting agents

1. Mepivacaine 3 %

2. Lidocaine 2%

Intermediate acting agents

1. Lidocaine 2% 1:100000 epi

2. Lidocaine 2% 1:50000 epi

3. Mepivacaine 2% 1:20000 neocobefrin

4. Prilocaine 4%

5. Articaine 4% 1:100000 epi

Long acting agents

1. Bupivacaine 0.5% 1:200000 epi