October 29th, 2010 by admin

Carbamazepine

The anticonvulsants, sometimes also called antiepileptics, belong to a diverse group of pharmaceuticals used in prevention of the occurrence of epileptic seizures. The goal of an anticonvulsant is to suppress the rapid and excessive firing of neurons that start a seizure. Failing this, a good anticonvulsant would prevent the spread of the seizure within the brain and offer protection against possible excitotoxic effects that may result in brain damage. An excellent anticonvulsant would have few serious side effects. However, no such drug exists.

Many anticonvulsants block Sodium (Na+) channels, Calcium (Ca2+) channels, AMPA receptors or NMDA receptors. Some anticonvulsants inhibit the metabolism of GABA or increase its release.

In the following list, the dates in parentheses are the earliest approved use of the drug.

Aldehydes

• Paraldehyde (1882). One of the earliest anticonvulsants. Still used to treat status epilepticus, particularly where there are no resuscitation facilities.

Aromatic allylic alcohols

• Stiripentol (2001 – limited availability). Indicated for the treatment of severe myoclonic epilepsy in infancy (SMEI).

Barbiturates

Barbiturates are drugs that act as central nervous system (CNS) depressants, and by virtue of this they produce a wide spectrum of effects, from mild sedation to anesthesia. The following are classified as anticonvulsants:

• Phenobarbital (1912). See also the related drug primidone.
• Methylphenobarbital (1935). Known as mephobarbital in the US. No longer marketed in the UK
• Metharbital (1952). No longer marketed in the UK or US.
• Barbexaclone (1982). Only available in some European countries.

Phenobarbital was the main anticonvulsant from 1912 till the development of phenytoin in 1938. Today, phenobarbital is rarely used to treat epilepsy in new patients since there are other effective drugs that are less sedating. Phenobarbital sodium injection can be used to stop acute convulsions or status epilepticus, but a benzodiazepine such as lorazepam, diazepam or midazolam is usually tried first. Other barbiturates only have an anticonvulsant effect at anaesthetic doses.

Benzodiazepines

The benzodiazepines are a class of drugs with hypnotic, anxiolytic, anticonvulsive, amnestic and muscle relaxant properties. The relative strength of each of these properties in any given benzodiazepine varies greatly and influences the indications for which it is prescribed. Long-term use can be problematic due to the development of tolerance and dependency. Of the many drugs in this class, only a few are used to treat epilepsy:

• Clobazam (1979). Notably used on a short-term basis around menstruation in women with catamenial epilepsy.
  Clonazepam (1974).
  Clorazepate (1972).

The following benzodiazepines are used to treat status epilepticus:

• Diazepam (1963). Can be given rectally by trained care-givers.
• Midazolam (N/A). Increasingly being used as an alternative to diazepam. This water-soluble drug is squirted into the side of the mouth but not swallowed. It is rapidly absorbed by the buccal mucosa.
• Lorazepam (1972). Given by injection in hospital.

Bromides

• Potassium bromide (1857). The earliest effective treatment for epilepsy. There would not be a better drug for epilepsy until phenobarbital in 1912. It is still used as an anticonvulsant for dogs and cats.

Carbamates

• Felbamate (1993). This effective anticonvulsant has had its usage severely restricted due to rare but life-threatening side effects.

Carboxamides

The following are carboxamides:

• Carbamazepine (1965). A popular anticonvulsant that is available in generic formulations.
  Oxcarbazepine (1990). A derivative of carbamazepine that has similar efficacy but is better tolerated.

Fatty acids

The following are fatty-acids:

• The valproates — valproic acid, sodium valproate, and divalproex sodium (1978).
  Vigabatrin (1989).
  Progabide
  Tiagabine (1997).

Vigabatrin and progabide are also analogs of GABA.

Fructose derivatives

• Topiramate (1995).

Gaba analogs

• Gabapentin (1993).
  Pregabalin (2004).

Hydantoins

The following are hydantoins:

• Ethotoin (1957).
  Phenytoin (1938).
  Mephenytoin
  Fosphenytoin (1996).

Oxazolidinediones

The following are oxazolidinediones:

• Paramethadione
  Trimethadione (1946).
  Ethadione

Propionates

• Beclamide

Pyrimidinediones

• Primidone (1952).

Pyrrolidines

• Brivaracetam
  Levetiracetam (1999).
  Seletracetam

Succinimides

The following are succinimides:

• Ethosuximide (1955).
  Phensuximide
  Mesuximide

Sulfonamides

• Acetazolamide (1953).
  Sulthiame
  Methazolamide
  Zonisamide (1990).

Triazines

• Lamotrigine (1991).

Ureas

• Pheneturide
  Phenacemide

Valproylamides (amide derivatives of valproate)

• Valpromide
  Valnoctamide

References

• Drug Reference for FDA Approved Epilepsy Drugs
• UK Anti-Epileptic Drugs List

Links

• eMedicine: Antiepileptic Drugs: an overview
• NINDS: Anticonvulsant Screening Program
• Use of Anticonvulsants in Pharmacotherapy of Bronchial Asthma
• MDNG: Anticonvulsants and Bone Health

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia.

October 17th, 2010 by admin

An anticoagulant is a substance that prevents coagulation; that is, it stops blood from clotting. A group of pharmaceuticals called anticoagulants can be used in vivo as a medication for thrombotic disorders. Some chemical compounds are used in medical equipment, such as test tubes, blood transfusion bags, and renal dialysis equipment..

As medications

Anticoagulants are given to people to stop thrombosis (blood clotting inappropriately in the blood vessels). This is useful in primary and secondary prevention of deep vein thrombosis, pulmonary embolism, myocardial infarctions and strokes in those who are predisposed.

Vitamin K antagonists

The oral anticoagulants are a class of pharmaceuticals that act by antagonizing the effects of vitamin K. It is important to note that they take at least 48 to 72 hours for the anticoagulant effect to develop fully. In cases when an immediate effect is required, heparin must be given concomitantly. Generally, these anticoagulants are used to treat patients with deep-vein thrombosis (DVT), pulmonary embolism, atrial fibrillation, and mechanical prosthetic heart valves.

These oral anticoagulants are used widely as poisons for mammalian pests, especially rodents.

The most important oral anticoagulants are:

• Warfarin (Coumadin). This is the main agent used in the U.S. and UK
• Acenocoumarol and phenprocoumon This is used more commonly outside the U.S. and the UK
• Phenindione

Heparin and derivative substances

Heparin is a biological substance, usually made from pig intestines. It works by activating antithrombin III, which blocks thrombin from clotting blood. Heparin can be used in vivo (by injection), and also in vitro to prevent blood or plasma clotting in medical devices. Vacutainer brand test tubes containing heparin are usually colored green.

Low molecular weight heparin is a more highly processed product that is useful as it does not require monitoring of the APTT coagulation parameter (it has more predictable plasma levels) and has less side effects.

Fondaparinux is a synthetic sugar composed of the five sugars (pentasaccharide) in heparin that bind to antithrombin. It is a smaller molecule than low molecular weight heparin.

Direct thrombin inhibitors

Another type of anticoagulant is the direct thrombin inhibitors. Current members of this class include argatroban, lepirudin, and bivalirudin. An oral direct thrombin inhibitor, ximelagatran (Exanta®) may replace warfarin for some indications. It is awaiting Food and Drug Administration (FDA) approval.

Anticoagulants outside the body

Laboratory instruments, test tubes, blood transfusion bags, and medical and surgical equipment will get clogged up and become nonoperational if blood is allowed to clot. Chemicals can be added to stop blood clotting. Apart from heparin, most of these chemicals work by binding calcium ions, preventing the coagulation proteins from using them.

• EDTA is denoted by mauve or purple caps on Vacutainer brand test tubes. This chemical strongly and irreversibly binds calcium. It is in a powdered form.
  Citrate is usually in blue Vacutainer tube. It is in liquid form in the tube and is used for coagulation tests, as well as in blood transfusion bags. It gets rid of the calcium, but not as strongly as EDTA. Correct proportion of this anticoagulant to blood is crucial because of the dilution. It can be in the form of sodium citrate or ACD.
  Oxalate has a similar mechanism to citrate. It is the anticoagulant used in fluoride (grey top) tubes.

Acest articol conţine materiale traduse şi adaptate din Wikipedia de Nicolae Sfetcu sub licenţă gratuită GNU.