Cabergoline (brand names Dostinex® and Cabaser®), an ergot-derivative, is a potent dopamine receptor agonist on D2-Receptors. It also acts on dopamine-receptors in lactophilic hypothalamus cells and causes thereby a suppression of the prolactin-production in pituitary gland.

Pharmacokinetics

Following an oral single dose the drug is resorbed within 0.5 to 4 hours from the GI-Tract with considerable interindividual differences. Meals do not alter the absorption characteristic. Human bioavailibility was not determined, because the drug is intended for oral use only. In mice and rats the absolute bioavailability was 30 and 63%, respectively. Cabergoline is rapidly and to a great extend metabolized in the liver and excreted in bile and far less in urine. All metabolites are less active than the parental drug or inactive. The human elimination halflife is estimated to be 63 to 68 hours in patients with M. Parkinson and 79 to 115 hours in patients with pituitary tumors.

Carcinogenity

In rodents a dose dependent increase in malignant tumors has been found. They are thought to be species-specific. No clinical data exists on carcinogenity in humans.

Uses

Monotherapy of Morbus Parkinson in the early phase.
Combination therapy of Morbus Parkinson in the progressive phase together with levodopa and a decarboxylase-inhibitor like carbidopa.
Adjunctive therapy of prolactin-producing tumors of the pituitary gland (microprolactinomes).
In some countries also : ablactation and dysfunctions associated with hyperprolactinemia (amenorrhea, oligomenorrhea, anovulation, und galactorrhea).

Off-Label/Recreational Uses

It has at times been used as an adjunct to SSRI antidepressants as there is some evidence that it counteracts certain side effects of those drugs such as reduced libido and anorgasmia. It also has been suggested online that it has a possible recreational use in reducing or eliminating the male refractory period.

Contraindications and Precautions

Hypersensitivity to ergot-derivatives
Pediatric Patients (no clinical experience)
Severely impaired liver function or cholestasis
Comedication with drugs metabolized mainly by CYP P450 such as erythromycin and ketoconazole, because increased plasma levels of cabergoline may result.
Cautions : severe cardiovascular disease, Raynaud's Syndrome, gastroduodenal ulcers, active gastrointestinal bleeding, hypotension.

Pregnancy and Lactation

Pregnancy : Approximately 100 female patients became pregnant under therapy with cabergoline for hyperprolactinemic conditions. The incidence of spontanous aborts and congenital abnormalities was comparable to nontreated patients. Nonetheless womem, wishing to become pregnant, should wait a safety period of 4 weeks after discontinuation of cabergoline. Patients becoming pregant under therapy should terminate cabergoline immediately, if possible.
Lactation : In rats cabergoline was found in the maternal milk. Since it is not known, if this effect is also seen in humans, lactating women should not be treated.

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Metoclopramide
From Gale Encyclopedia of Cancer, by M.Sc. Alison McTavish

Definition

Metoclopramide (Reglan, Octamide, Maxeran) is a drug used to prevent the nausea and vomiting caused by cancer chemotherapy.

Purpose

Nausea and vomiting are among the most common side effects of cancer chemotherapy. They are also among the most unpleasant and upsetting side effects for patients. If left untreated, persistent nausea and vomiting can lead to dehydration, dental decay, digestive abnormalities, and nutritional deficiencies. In addition, persistent vomiting may force some patients to stop taking their chemotherapy and risk a recurrence of their cancer. It is therefore very important that these symptoms be adequately treated.

The nausea and vomiting that occurs with chemotherapy is often divided into three types: anticipatory, acute, and delayed. Anticipatory nausea and vomiting usually occurs before or during chemotherapy. These symptoms are thought to be caused by anxiety, and often occur in patients who have been previously treated with very toxic chemotherapy. Acute nausea and vomiting occurs within a few minutes to several hours after drug administration and usually stops within 24 hours. Delayed nausea and vomiting occurs several hours after chemotherapy, and can last several days.

Description

For the majority of patients, nausea and vomiting can be successfully treated with antiemetic medication. Metoclopramide is one of the most widely used and effective antiemetics for treating the delayed nausea and vomiting caused by chemotherapy. It has been used since the 1980s, and works in two ways. It affects a part of the brain known to trigger vomiting, and also affects the speed of intestinal motion. As a result, the stomach empties into the intestines more quickly, and the contents of the intestines move more quickly in the correct direction.

Metoclopramide is most often used in patients taking cisplatin (Platinol) chemotherapy. Cisplatin is used to treat a wide range of cancers including bladder cancer, ovarian cancer and non-small cell lung cancer. Compared with other cancer chemotherapy, cisplatin is often considered to cause the most severe nausea and vomiting. For 60% to 70% of patients taking cisplatin, however, metoclopramide provides control of nausea and vomiting.

Recommended dosage

Although metoclopramide can be taken either orally or intravenously, cancer patients on chemotherapy usually receive the drug intravenously. Metoclopramide is usually given 30 minutes before chemotherapy, and then two more times after chemotherapy at two hour intervals.

The recommended dose varies from patient to patient, and depends on both the severity of nausea and vomiting, and on the toxicity of the drug. A higher dose will be given to patients with severe symptoms. Higher doses will also be given to patients receiving drugs such as cisplatin that are known to cause severe nausea and vomiting. Some patients receiving cisplatin may be given a combination of three different drugs to help combat their nausea: metoclopramide, dexamethasone (Dexone), and lorazepam (Ativan). The three work on different areas of the body and produce a greater effect together than they do when given separately.

Precautions

Metoclopramide can cause sleepiness and lack of concentration. Patients should avoid tasks that require mental alertness such as driving or operating machinery. Patients should also be aware that metoclopramide may enhance their response to alcohol and drugs that depress the central nervous system. Because metoclopramide can cause depression, patients with a history of serious clinical depression should take this drug only if absolutely necessary.

Metoclopramide can make the symptoms of Parkinson's disease worse, and patients with a history of seizures should not take metoclopramide, because the frequency and severity of the seizures may increase. The drug should also not be used in patients with intestinal problems such as bleeding, tears, or blockages. The safety of metoclopramide for pregnant women or children is unknown. The drug is found in the breast milk of lactating mothers.

Side effects

The most frequent side effects of metoclopramide are restlessness, drowsiness and fatigue. These occur in about 10% of patients. Less common side effects include insomnia, headache, and dizziness. These occur in only 5% of patients. Feelings of anxiety or agitation may also occur, especially after a rapid intravenous injection of the drug. Some women may experience menstrual irregularities.

Metaclopramide therapy can cause some patients to make abnormal involuntary movements, a condition known as dyskinesia. These reactions are most common in young adults of 18-30 years of age, and often disappear about a day after the patient stops taking the drug. Among geriatric patients, particularly women, dyskinesia sometimes develops when patients stop taking metoclopramide after long term treatment.

Interactions

Patients who are also taking cabergoline (Dostinex), a drug used to treat hormonal problems and Parkinson's disease, should not take metoclopramide. Because metoclopramide affects the functioning of the intestines, it can interfere with the absorption of certain drugs. The effect of digoxin (Lanoxin), for example, may be reduced, whereas the effects of other drugs like aspirin, cyclosporine (Neoral, Sandimmune, SangCya) and tetracycline (Minocin, Vibramycin) may be enhanced.

KEY TERMS

Antiemetic

A drug that prevents nausea and vomiting.

Dyskinesia

A condition that causes a person to make abnormal, involuntary movements.

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