Drug+Action+&+Adverse+Reaction

= Drug Action and Adverse Reaction = Amber and Candice will work on this page together

There are many mechanisms of drug action. **First we will start with the drug receptors:** 1.Ion channel linked receptors: -Two general classes: voltage gated and ligand gated

a. Voltage gated=activated by alterations in membrane voltage. Voltage gated NA+ channels open when the membrane is depolarized to a threshols potential and contribute to furthermembrane depolarization by allowing NA+ influx into the cell.

b. Ligand gated= activated in reponse to the binding of specific ligands, such as neurotransmitters or drugs. Ligand gated ion channels can either depolarize or hyperpolarize the cell membrane.

2. G protein linked receptors: AKA “metabotropic receptors.” Target for approximately half of all nonantimicrobial perscription drugs. Greatly amplifies extracellular biological signals because they activate G proteins, which activate ion channels or more commonly other enzymes, leading to the introduction or formation of a host of internal second messengers for each extracellular signal molecule detected.

3. Enzyme linked receptors: Has only one transmembrane domain per protein subunit, with an enzymatic catalytic site on the cytoplasmic side of the receptor. Dimerization of activated receptors usually provides the conformational change required for expression of enzymatic activity.

4. Intracellular receptors: Lipophilic substances, such as sex steroids, mineralcorticoids, glucocorticoids, thyroid hormones, and vitamin D derivatives which are capable of crossing the plasma membrane activate specific nuclear receptors that influence DNA transcription.
 * Next lets take a look at the drug-binding forces:** 1. Covalent bonds: arise from the sharing of electrons by a pair of atoms. Generally not involved in drug-receptor interactions and are the strongest type of bond.

2. Ionic bonds: result from electrostatic attraction between ions of opposite charge and initiates many drug-receptor combinations.

3. Cation ”Pi sign” interactions: Benzene and similar aromatic compounds are hydrophobic solvents but their “Pi sign” electron clouds are capable of interacting with positively charged ions. Amino acids with aromatic side groups retain this ability.

4. Hydrogen bonds: a type of interaction between polar molecules. Much weaker than ionic bonds.

5. Van der waals: the weakest interaction that develop when two atoms are placed in close proximity **Drug response relations:** Antagonis= reverse action of agonist
 * Agonist=Action

Agonist are drugs that bind to a receptor and draw out a certain response from the tissue. Antagonists are drugs that bind to a receptor and blocks or hinders the affect of a agonists.

** Dose Responce relationships: ** A fundamental aspect of drug action is the relationship between the dose given and the effect that it has. When a drug is administerd into tissue, it binds to its receptors. each muscle cell may require a minimal number of receptors to be occupied before it contracts. The lowest concentration to draw out a responce is called the //threshold concentration//. The maximal muscle responce for a drug is he //ceiling effect//. When concentrations are high the receptors become saturated and futher administration of the drug has no influence. It like if you have a sponge that has been left in sink full of water.. it can only abosorb so much regardless of it swimming in a sink of water it has soaked up all it can. The ideal range for a drug is between the threshold and ceiling effect. To obtain a curve responce we have to look at the concentration vs the degree of the responce. ||

Extension effects:Drugs are made with a specific amount of "working power" of theraputic dosage. If they there were made with the full amount of working power then this could result in toxic and dangerous outcomes.
 * Adverse Drug reactions:**

Side effects:is a dose related reaction that is not the desired theraputic out come. ex you take ibuprofen it takes your headache away, but upsets your stomach. Idiosyncratic reactions: abnormal responce to a drug. Depending on how much of the drug is given reactions are unpredictable, because of a genetic trait that is unkown to the person. Drug allergy:is a adverse immunologic response to a drug they are neither predictible or dose related. The allergy is caused by the persons own immune responce. 4 types of allergy reactions: Type I= anaphylactic responces,immediate response w/in mins or hours of takin the drug TypeII=cytotoxic reactions caused by circulating anti-bodies(IgG and IgM) TypeIII=immune-complex occur when soluble antigen- antibody complexes form in intrastitial spaces TypeIV= usually delayed reactions they are cell mediated