Carbamazepine for Trigeminal Neuralgia

• Trigeminal neuralgia (TN), also known as tic douloureux, is a distinctive facial pain syndrome that may become recurrent and chronic. 
• It is characterized by unilateral pain following the sensory distribution of cranial nerve V (typically radiating to the maxillary or mandibular area in 35% of affected patients) and is often accompanied by a brief facial spasm or tic.1

Carbamazepine

• The only approved medication by FDA for the treatment of Trigeminal Neuralgia 
• Pharmacologic therapy is the initial treatment of most patients with classic TN (ie, TN that is idiopathic or caused by neurovascular compression). 
• Surgery is reserved for patients who are refractory to medical therapy.
• Carbamazepine is the best studied treatment for classic TN and is established as effective. 
• Side effects can be a problem but are generally manageable, particularly if low doses are prescribed initially with gradual titration.2

Dosing

Ref: Clinical Pharmacokinetics Pharmacy Handbook,2015

Ref: https://www.drugs.com/dosage/carbamazepine.html

Therapeutic Drug Monitoring(TDM)

• Sampling time: 30 minutes before the next dose.

 Ref: Clinical Pharmacokinetics Protocol. PSD, Sabah State Health Department. 

Ref: Clinical Pharmacokinetics Pharmacy Handbook, 2015

Toxic level

• Lexicomp: >15mcg/ml
• Medscape: The toxic concentration/critical laboratory value is greater than 30-40 mg/L

Ref: Clinical Pharmacokinetics Pharmacy Handbook, 2015

References

1. http://emedicine.medscape.com/article/1145144-overview
2. www.uptodate.com
3. Clinical Pharmacokinetics Pharmacy Handbook, 2015
4. https://www.drugs.com/dosage/carbamazepine.html
   

Interactions: Kalimate

Dietary

• Mix the sodium polystyrene sulfonate powder with water, or with honey or jam to make it taste better.
• Avoid inhaling the oral powder while you are preparing a dose.
• Do not mix the powder with any juice or other liquid that contains potassium, such as orange juice.
• The potassium in foods will bind with the resin preventing adequate potassium removal from patients with hyperkalemia.

Supplementation

• Sodium polystyrene sulfonate can bind to calcium, iron, magnesium, and other minerals in the gastrointestinal tract.
• This may inactivate both sodium polystyrene sulfonate and the mineral it binds to and reduce the effectiveness of both medications.
• To avoid or minimize the interaction, the dosing times of sodium polystyrene sulfonate and multivitamin with minerals should be separated by several hours

Antacids & Laxatives

• alkalosis following concurrent administration of cation-exchange resins and non-absorbable cation-donating antacids and laxatives such as magnesium hydroxide and aluminium carbonate.
• Intestinal obstruction due to concretions of aluminium hydroxide has been reported when aluminium hydroxide has been combined with the resin (sodium form).
• Management: Monitor for signs/symptoms of intestinal obstruction with concomitant use of calcium polystyrene sulfonate and aluminum hydroxide.
• Adequate fluid intake, laxative use, alternative antacid agents, and/or limiting duration of therapy may help reduce risks

Sorbitol

• Concomitant use of Sorbitol with calcium polystyrene sulfonate is not recommended due to cases of intestinal necrosis and other serious gastrointestinal adverse reactions, which may be fatal

References:

1. Resonium Information Leaflet
2. https://www.drugs.com/food-interactions/sodium-polystyrene-sulfonate.html?professional=1
3. https://www.medicines.org.uk/emc/medicine/6739