1. Clinical Overview
Recombinant follicle stimulating hormone (rFSH) is a highly purified, non-urinary derived gonadotropin produced by recombinant DNA technology in Chinese Hamster Ovary (CHO) cells. It is structurally and functionally identical to endogenous human FSH, consisting of two non-covalently linked, glycosylated subunits (alpha and beta). It is a critical agent in controlled ovarian stimulation (COS) protocols for assisted reproductive technology (ART) and for ovulation induction in anovulatory women. In the Indian context, it is a cornerstone of infertility treatment, available in both vial and pen injector forms.
| Onset | Duration | Bioavailability |
|---|---|---|
| Pharmacodynamic effects (increase in estradiol) are typically observed within 24-48 hours of administration. | The biological effect persists for approximately 24 hours, necessitating daily administration during treatment cycles. | Approximately 70-80% after subcutaneous injection. |
2. Mechanism of Action
Recombinant FSH binds to specific FSH receptors located on the granulosa cells of the ovarian follicles. This binding activates the adenylate cyclase system, increasing intracellular cAMP. This cascade stimulates follicular growth and maturation, promotes aromatase activity for the conversion of androgens to estrogens (primarily estradiol), and increases inhibin B production.
3. Indications & Uses
- Ovulation induction in anovulatory or oligo-ovulatory women (e.g., with Polycystic Ovary Syndrome - PCOS) who are unresponsive to clomiphene citrate.
- Controlled ovarian stimulation for the development of multiple follicles in women undergoing assisted reproductive technologies (ART) such as In Vitro Fertilization (IVF) or Intracytoplasmic Sperm Injection (ICSI).
4. Dosage & Administration
Adult Dosage: HIGHLY INDIVIDUALIZED. **Ovulation Induction:** Starting dose is typically 75-150 IU SC daily, adjusted based on response. **ART (IVF/ICSI):** Starting dose ranges from 150-300 IU daily, often in combination with other hormones (GnRH agonists/antagonists). The 75IU vial is used for precise dose titration.
Administration: For subcutaneous injection into the abdominal wall or anterior thigh. Rotate injection sites. Reconstitute the lyophilized powder with the provided solvent (if using vial). Pre-filled pens are also available. Administer at approximately the same time each day. Strict aseptic technique must be followed.
5. Side Effects
Common side effects may include:
- Injection site reactions (pain, redness, bruising).
- Headache.
- Mild to moderate ovarian enlargement with abdominal pain/discomfort.
- Nausea.
- Breast tenderness.
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Clomiphene Citrate | May have synergistic effect, increasing follicular response and OHSS risk. | Moderate |
| GnRH Agonists (e.g., Leuprolide) | Used in combination for pituitary down-regulation in ART cycles. Synergistic. | Low (managed protocol) |
| GnRH Antagonists (e.g., Cetrorelix, Ganirelix) | Used in combination to prevent premature LH surge. No significant PK interaction. | Low (managed protocol) |
| hCG (Human Chorionic Gonadotropin) | Used to trigger final oocyte maturation after FSH stimulation. Sequential use is standard. | Low (managed protocol) |
7. Patient Counselling
- DO learn proper subcutaneous injection technique from your healthcare provider.
- DO rotate injection sites daily.
- DO keep all monitoring appointments for ultrasound and blood tests.
- DO report severe abdominal pain, nausea, vomiting, or rapid weight gain immediately.
- DONT change the dose without consulting your doctor.
- DONT use if the solution is discolored or contains particles.
- DONT mix with other medications in the same syringe unless instructed.
8. Toxicology & Storage
Overdose: Manifestations would be an exaggeration of pharmacological effects: severe ovarian hyperstimulation syndrome (OHSS) with massive ovarian enlargement, ascites, hydrothorax, hemoconcentration, thromboembolism, and electrolyte imbalance.
Storage: Store unopened vials/pens at 2°C to 8°C (in a refrigerator). Do not freeze. Protect from light. After reconstitution (for vials), use immediately. For some pre-filled pens, storage after first use may be allowed at room temperature (not above 25°C) for a limited time (e.g., 28 days) – refer to specific brand instructions. Keep out of reach of children.