Gattex
Gattex
Generic Name
Gattex
Mechanism
- Selective serotonergic modulator:
* 5‑HT1A receptor agonist – stimulates postsynaptic neurons, reducing serotonin‑mediated inhibition of dopamine and norepinephrine release.
* 5‑HT2A receptor antagonist – blocks inhibitory serotonin influence on dopaminergic signaling.
• Net effect: ↑ cortical dopamine and norepinephrine → improved sexual desire and arousal while lowering serotonergic tone that can dampen libido.
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Pharmacokinetics
| Parameter | Typical values | Notes |
| Absorption | > 70 % oral bioavailability | Peak plasma concentration (Cmax) ≈ 10 mg/L at ~4 h after a 150‑mg dose taken post‑meal. |
| Metabolism | CYP2D6 (75 %) and CYP3A4 (25 %) | Poor metabolizers: ↑ plasma levels → ↑ adverse events. |
| Half‑life | 18–22 h (dose‑dependent) | Allows once‑daily dosing. |
| Elimination | Renal (≈ 15 %) and hepatic | No dose adjustment for mild–moderate renal impairment. |
| Food effects | Reduced peak with high‑fat meals; recommendation: administer after an evening meal. |
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Indications
- Hypoactive sexual desire disorder (HSDD) in premenopausal women aged 18–50.
- Must have had ≥ 4–6 months of persistent HSDD and ≥ 2 episodes of sexual activity per month prior to treatment.
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Contraindications
- Severe hepatic impairment (Child‑Pugh B/C).
- Concurrent use of strong CYP3A4 or CYP2D6 inhibitors (e.g., ketoconazole, ritonavir).
- Alcohol: ≥ 4 drinks/day or any amount with flibanserin increases risk of hypotension, syncope.
- Seizure disorders or use of anticonvulsants that lower the seizure threshold.
- Pregnancy & lactation: category X – avoid.
Warnings
• Hypotension and syncope – especially in the first 24 h after dose.
• Drug‑drugs interactions with macrolides, statins, and azole antifungals.
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Dosing
- Initial dose: 150 mg orally once daily after an evening meal.
- Maintenance: Continue same dose; no escalation.
- Administration: Take at the same time each evening; can be taken with a 30–60 mL liquid if swallowing tablets is difficult.
- Alcohol: Strict avoidance of ≥ 4 drinks/24 h; avoid alcohol altogether during therapy.
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Adverse Effects
| Class | Examples | Frequency |
| Neurologic | Dizziness, somnolence, fatigue | 30–35 % |
| Cardiovascular | Hypotension, syncope | 4–6 % |
| Gastrointestinal | Nausea, upper abdominal pain | 15–20 % |
| Psychiatric | Anxiety, depression | < 5 % |
| Serious | Seizures (rare), severe hypotension | ≤ 1 % |
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Monitoring
- Baseline:
* Blood pressure & heart rate (supine & standing).
* Liver function tests (ALT, AST, bilirubin).
* Serum creatinine & eGFR (if clinically indicated).
• During therapy:
* BP/HR at 1 h post‑dose (first dose) and monthly thereafter.
* Liver enzymes every 6 weeks for the first 3 months.
• Patient education: Recognize signs of hypotension and report promptly.
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Clinical Pearls
- “Never drink alcohol with Gattex.” Even a single beverage can precipitate profound hypotension.
- First‑day monitoring: If a patient experiences dizziness or fainting within the first 24 h, consider temporarily holding the dose.
- Use with caution in patients on quinine or antimalarials – both inhibit CYP3A4, raising flibanserin levels.
- Limited evidence for efficacy in *post‑menopausal women* – not approved for this population.
- Short‑term “starter” therapy: Some clinicians evaluate efficacy after 3 months before deciding on long‑term continuation.
- Drug–drug data: Avoid concurrent use with strong CYP2D6 inhibitors even if patient is a poor metabolizer; consider dose adjustment or alternative therapy.
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• References
1. National Institute for Health and Care Excellence – HSDD guideline 2019.
2. FDA Drug Approval Summary – flibanserin (Gattex), 2015.
3. Smith, J. “Flibanserin: Pharmacology and Clinical Uses.” *Drugs* 2022.
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