Sinemet

Antiparkinsonian Drug

Drug class: Dopaminergic Antiparkinsonian Agent

Levodopa and Carbidopa (SINEMET)（中文：左旋多巴和卡比多巴）

Pronunciation

Sinemet 25 100

Sinemet CR 50 200

Common Strengths of Sinemet

• 25 mg carbidopa and 100 mg levodopa
• 25 mg carbidopa and 200 mg levodopa
• 25 mg carbidopa and 250 mg levodopa
• 50 mg carbidopa and 200 mg levodopa in extended-release formulation

Drug Trade Names

• Sinemet, Sinemet CR (controlled release)

Drug Usage

Sinemet treats symptoms of Parkinson's disease, including tremors, stiffness, and difficulty with movement. It does not cure the disease but helps manage its symptoms.

Sinemet is a medication that combines two active ingredients: carbidopa and levodopa.

It is primarily used to treat Parkinson's disease and alleviate related symptoms including muscle stiffness, tremors and spams.

Mechanism of Action

Carbidopa inhibits the enzyme aromatic L-amino acid decarboxylase, preventing the peripheral conversion of levodopa to dopamine before it crosses the blood-brain barrier. This allows for more levodopa to reach the brain, enhancing its therapeutic effects while reducing side effects like nausea.

Route of Administration

• Oral tablets (immediate release and extended release)

Dosages

Individualized Dosage: The dosage of Sinemet must be carefully titrated for each patient. Initial dosages typically range from Sinemet 25/100 mg to higher strengths, depending on individual needs and responses.

Side Effects

Frequency	Adverse reactions
Common Side Effects	Nausea, vomiting, constipation
	Sleep problems and unusual dreams
	Dizziness or light-headedness
Serious Side Effects	Neuroleptic malignant syndrome (NMS)
	Hallucinations or severe mood changes
	Uncontrolled movements or muscle contractions

Pharmacokinetics

The onset of action for Sinemet can range from 10 minutes to 2 hours, with the effect lasting approximately 5 hours.

Drug Precautions

Pregnancy

Use during pregnancy only if clearly needed; potential risks should be discussed with a healthcare provider.

Breastfeeding

Caution is advised as both components can pass into breast milk; consult a doctor before use.

Drug Monitoring Items

• Monitoring During Adjustment:
  • Early signs of excessive dosage include involuntary movements like blepharospasm, which may indicate the need for dosage reduction.
• Regular monitoring of blood pressure, renal function, and liver function test is recommended due to potential side effects and interactions.
• Sinemet can lead to several side effects that require monitoring:
  • Dyskinesias: Abnormal involuntary movements are common and may necessitate dose adjustments
  • Psychiatric Symptoms: Increased urges for gambling or hypersexuality may develop;
  • Neuroleptic Malignant Syndrome (NMS): Abrupt discontinuation or dose reduction can lead to symptoms resembling NMS, including fever, muscle rigidity, and altered consciousness.

Drug Interactions

Avoid concurrent use with non-selective MAO inhibitors due to risk of severe interactions.

• Dopamine Antagonists:
  • Drugs like haloperidol, metoclopramide, and phenothiazines can inhibit dopamine in the brain, reducing the effectiveness of Sinemet and potentially worsening Parkinson's sypmtoms
• Tricyclic Antidepressants (TCAs):
  • Concurrent use may heighten the risk of hypertension and dyskinesia. Examples include amitriptyline and imipramine
• Iron Supplements:
  • Iron can form complexes with levodopa, reducing its absorption and effectiveness. It is advisable to separate the administration of iron supplements from Sinemet by several hours
• Dopamine-Depleting Agents: Medications like reserpine or tetrabenazine are not recommended with Sinemet due to their potential to diminish its therapeutic effects

FAQ

How Should I Take the Tablet?

Take Sinemet on an empty stomach or with low-protein food if necessary; avoid high-protein meals that can reduce absorption.

What Should I Avoid While Taking?

Avoid taking iron supplements within two hours of Sinemet and high-protein meals that may interfere with its effectiveness.

What Happens if I Miss a Dose?

If you miss a dose, take it as soon as you remember unless it is close to the time for your next dose; do not double up on doses.