From the FDA Drug Label
Clinical Pharmacology ... Baclofen is rapidly and extensively absorbed and eliminated. The onset of action for Baclofen is not explicitly stated in the drug label.
- The label mentions that Baclofen is rapidly absorbed, but it does not provide a specific time frame for when it starts to take effect.
- No conclusion can be drawn about the exact timing of when Baclofen starts to take effect 1.
From the Research
Baclofen typically begins to work within 1-2 hours after taking an oral dose, with peak effects occurring around 2-3 hours after administration. However, patients may not experience the full therapeutic benefits for muscle spasticity until after several days or weeks of consistent use. The medication works by acting on GABA-B receptors in the spinal cord, inhibiting the transmission of signals that cause muscle contractions and reducing muscle tone and spasticity.
Key Points to Consider
- When starting baclofen, doctors usually prescribe a low initial dose (typically 5mg three times daily) and gradually increase it to minimize side effects like drowsiness, dizziness, and weakness 2.
- This gradual titration allows the body to adjust to the medication while finding the optimal therapeutic dose.
- Patients should take baclofen exactly as prescribed and not stop it abruptly, as sudden discontinuation can cause serious withdrawal symptoms including hallucinations, seizures, and increased spasticity.
- If baclofen doesn't seem to be working after several weeks of consistent use at an appropriate dose, patients should consult their healthcare provider rather than adjusting the dose themselves.
Administration and Pharmacokinetics
- Baclofen can be administered orally or intrathecally, with the latter method allowing for direct delivery to the spinal cord and potentially reducing side effects 3, 4.
- The pharmacokinetics of baclofen have been studied in both animal and human subjects, with results showing that the drug is rapidly absorbed and eliminated after oral administration 5.
- The bioavailability of oral baclofen is approximately 80%, with the majority of the drug being excreted in the urine 2.
Special Considerations
- Intrathecal baclofen therapy may be considered for patients with refractory spasticity who have not responded to oral medications 6.
- This approach allows for targeted delivery of the medication to the spinal cord, potentially reducing side effects and improving efficacy.
- However, intrathecal baclofen therapy requires careful patient selection and monitoring, as well as expertise in the placement and management of intrathecal pumps.