INTRODUCTION
Despite an increase in the usage of regional anesthesia for labor analgesia in recent years, systemic medications given via intramuscular or intravenous injections are still widely used. Many patients who neither want or need regional anesthesia techniques (intrathecal, epidural) find that these medications are a good option for the partial relief of their labor pain.

In helping patients to decide what type of technique is best suited for them, the difference between analgesia (decrease of pain or awareness of pain) and anesthesia (blocking of pain, usually with local anesthetics which results in numbness and lack of feeling) must be made clear. Intravenous medications are used to provide analgesia, not anesthesia. The amount of analgesia is limited by the side effects that occur with increasing dosages. Still, this is often adequate. It is important to note that there is no ideal, universal anesthetic or analgesia

TYPES OF SYSTEMIC MEDICATIONS
There are five classes, or types, of medications that are commonly utilized for systemic administration. This week we will discuss four of them and next week we will discuss the fifth and probably most important (narcotics).

The five categories are as follows:

• Narcotics
• Sedative Tranquilizers
• Dissociative/Amnestic Drugs
• Neuroleptanalgesia
• Antagonists

GENERAL COMMENTS
It is important to note that all medications given systemically do cross the placenta and thus are present to some extent in the bloodstream of the fetus. Therefore, these drugs all have the potential to depress the fetus in differing degrees. How much depression actually occurs depends on the drug chosen, the route by which it is administered, the timing of administration with regards to delivery of the baby and the presence of other obstetric complications.

NARCOTICS
Narcotics are usually considered the most effective of all the systemic medications. in addition, they are the most commonly used of all the five classes. This category includes such medications as Demerol, Fentanyl, Stadol (butorphanol) and Nubain. We'll cover this category in detail next week in part two of this feature.

In general, it is important to note that the narcotics represent one of the most powerful classes of analgesic agents that we utilize. Their usefulness is therefore only limited by the side effects that they cause. Said another way, these drugs are able to give complete analgesia (pain relief) but often only at the expense of respiratory depression, decreased ventilation, decreased blood pressure and obtunded reflexes. Obviously, this is not a desirable state for the mother or the baby. As a result, narcotics are utilized to reduce the pain associated with labor, not eliminate it. All the narcotics can reduce pain - the choice of which one to use is based on speed of onset, duration of action and side effects associated with the drug.

We'll cover more details, and specific drugs, in part two of this article.

SEDATIVE TRANQUILIZERS
This class of drugs must be explained with an important caveat. They do not provide any pain relief. What these drugs do accomplish is that they decrease anxiety and promote sleep (they make you drowsy). For some patients, this is all that is needed for a successful and more comfortable labor and delivery. Often, these drugs are used in conjunction with other medications to reduce the dosage required of each drug, thereby reducing the chance or severity of side effects.

Some of the drugs in this category, known as phenothiazines, are also antiemetics - meaning that they decrease the incidence of nausea and vomiting. This, in addition to their sedative properties, can often be a helpful and desired effect. Common drugs in the phenothiazine class are Largon and Phenergen. The effect on the fetus is minimal, but the drugs can cause a decrease in blood pressure so this should be monitored.

Another class of sedative tranquilizers are the barbiturates. Common drugs in this class are Seconal, Nembutal, and Amytal. These drugs were once very popular for use during early labor, but today they are not as widely used. The main reason is that they can depress the fetus, causing it to be very sedated as well. They also share the effect of phenothiazines of lowering blood pressure.

The benzodiazepines represent the third class of sedative tranquilizers and are perhaps the most commonly utilized of the three. Common drugs in this class are Diazepam (Valium), Lorazepam and Midazolam (Versed). These drugs have minimal effects on the mother and the fetus when used in small doses. In higher doses, they do cause respiratory depression in the mother and decreased heart rate variability in the fetus. It is important to also mention that these drugs, especially Versed, can cause amnesia - something that the mother may object to if she wishes to remember the birthing experience.