tetrahydrocannabinol

This should be delta-11 THC. This refers to the double bond in one of the rings in the structure.

Consulting the excellent text 'Chemical Aspects of Biosynthesis'' I find that THC is a product of mixed metabolism. Fusion of geranyl pyrophosphate and olivetol(2,4-hydroxy,5-pentylbenzoate) form the skeleton which is cyclised to form the final product.

Although i can't seem to name THC properly (IUPAC nomenclature is horrendous for multiple ring systems) I can give you the SMILE string:
c1c(CCCCC)cc(O)c2c1OC(C)(C){C@@H}3CCC(C)=C{C@@H}23

This should give the correct stereochemistry.

Tetrahydrocannabinol or THC is the active ingredient in cannabis. Its Chemical Formula is C₂₁H₃₀O₂. It consists of three aromatic rings with a hydrocarbon tail.

The typical effects of THC are placidity and calmness, reduced blood pressure, poor muscle coordination. Its effects are similar to most barbiturates, and under a large dosage has been known to cause hallucinations. THC is not physically addictive, and it is believed to have certain medical benefits, but there are conflicting results as to the validity of this.

Most of the information here is paraphrased from www.lycaeum.org

           H      (CH2)4CH3
            \    /
             C==C
            /    \
        HO-C      C-H
           \\    // 
      H  H   C--C
       \  \ /    \
        C--C      O
      //    \    /
  H3C-C      C--C-CH3
       \    / \  \
      H-C--C-H H  CH3
        |  |
        H  H

     CH3
      |
      C
     / \\
    C   C    OH
    |   |     |
    C   C     C
     \ / \\ / \\
  H3C C    C    C
     \|    ||   |
      C    C    C     CH2     CH2
     / \  / \ // \   /   \   /   \
  H3C   O    C    CH2     CH2     CH3


Delta 9 - Tetrahydrocannabinol.

     CH3
      |
      C
     / \\
    C   C    OH
    |   |     |
    C   C     C
     \ / \\ / \\
  H3C C    C    C
     \|    |    |
      C    C    C     CH2     CH2
    //    / \ // \   /   \   /   \
  H2C   OH   C    CH2     CH2     CH3

Cannabidiol.

      OH
      ||
      C
     / \
    C   C    OH
    |   |     |
    C   C     C
     \ / \\ / \\
  H3C C    C    C
     \|    ||   |
      C    C    C     CH2     CH2
     / \  / \ // \   /   \   /   \
  H3C   O    C    CH2     CH2     CH3

Hydroxyhexahydrocannabinol.

Delta-trans-tetrahydrocannabinol, in capsule form more commonly known as dronabinol and sold as Marinol by Roxane Laboratories, is federally recognized as an appetite stimulant and anti-nausea/vomiting (antiemetic) agent (though some research indicates it is useful as an anti-glaucoma agent as well). It is available only through special prescription to treat persons suffering from chemotherapy- or radiation-related nausea, and to treat people suffering from AIDS-related anorexia. The FDA approved it for use as an antiemetic for chemotherapy patients in 1985 and as an appetite stimulant for AIDS patients in 1992.

Dronabinol has a complicated effect on the central nervous system, but it basically suppresses the neural impulses associated with nausea and stimulates the appetite (sometimes quite dramatically). As an appetite stimulant, a typical effective dose is 5 milligrams/day (2.5 mg an hour before lunch and dinner), though in clinical trials the dose ranged from 2.5-20 mg/day. As an antiemetic, total daily dosages range from 2.5-40 mg/day. Antiemetic doses are administered every four to six hours and seem to work best for people undergoing chemotherapy for lymphoma.

Side effects of dronabinol can include sleepiness, dizziness, confusion, and rapid heartbeat. Extreme overdoses can cause panic attacks, seizures in epileptics, and possibly hallucinations. Long-term use can possibly result in psychological addiction. Abrupt discontinuation of the drug can cause symptoms such as irritability, insomnia and sweating. In animal studies, dronabinol caused stillbirths and pup mortality, so it's recommended that pregnant women avoid the drug.

References:

Budavari, Susan, ed. 1989. The Merck Index: An Encyclopedia of Chemicals, Drugs and Biologicals. Rahway, NJ, Merck & Co.

Simpson, Beryl Brintnall and Molly Conner-Ogorzaly. 1986. Economic Botany: Plants in Our World. New York, NY, McGraw-Hill Publishing Co.

1995 Physician's Desk Reference ©. Montvale, NJ, Medical Economics Data Production Company.