Norprolac (Quinagolide)

Quinagolide acts on the dopaminergic pathway to reduce prolactin production, and is indicated for the following hyperprolactinemia‑related conditions.

• Hyperprolactinemia: reduces serum prolactin levels and restores normal menstrual cycles.
• Prolactin‑producing pituitary adenomas (prolactinomas): shrinks tumor size and normalizes prolactin secretion.
• Infertility related to hyperprolactinemia: improves ovulation and fertility outcomes by lowering prolactin.
• Amenorrhea due to elevated prolactin: reestablishes regular menses.

• Quinagolide selectively stimulates dopamine D2 receptors in the anterior pituitary lactotroph cells. Activation of these Gi‑protein coupled receptors inhibits adenylate cyclase activity, decreasing cyclic AMP formation and suppressing prolactin gene transcription and release. The resulting reduction in circulating prolactin restores normal hypothalamic‑pituitary‑gonadal feedback, alleviating symptoms associated with hyperprolactinemia. By maintaining low prolactin concentrations, the drug also diminishes the inhibitory effect of prolactin on gonadotropin‑releasing hormone, thereby supporting normal gonadal function.

Quinagolide may cause a range of adverse reactions, which are generally classified by frequency and severity.

Common Side Effects

• Nausea: mild to moderate gastrointestinal upset.
• Headache: transient cranial pain.
• Dizziness: sensation of light‑headedness, especially on standing.
• Fatigue: reduced energy levels.
• Dry mouth: decreased salivation.
• Abdominal pain: intermittent stomach discomfort.

Serious or Rare Side Effects

• Valvular heart disease: rare cardiac valve abnormalities.
• Psychiatric disturbances: depression, anxiety, or hallucinations.
• Severe hypotension: marked drop in blood pressure causing syncope.
• Pulmonary hypertension: elevated pressure in pulmonary arteries.

When prescribing Quinagolide, clinicians should consider several precautionary measures to ensure safe use.

• Cardiovascular assessment: evaluate for pre‑existing valvular disease or hypertension.
• Psychiatric history: screen for depression, anxiety, or psychosis.
• Pregnancy status: avoid use unless benefits outweigh risks; limited data available.
• Breastfeeding: discontinue if mother is nursing, as drug may pass into milk.
• Concomitant medications: review for drugs that affect dopamine pathways or blood pressure.
• Store at ambient temperature: keep below 25 °C, in original packaging, protected from moisture and light.

Quinagolide can interact with other medicines, altering its efficacy or safety profile.

Major Interactions (Avoid)

• Antipsychotics (e.g., haloperidol, risperidone): dopamine antagonists may counteract Quinagolide’s effect.
• Ergot derivatives (e.g., bromocriptine): additive risk of cardiovascular toxicity.
• Certain antihypertensives (e.g., alpha‑blockers): may cause severe hypotension.
• Macrolide antibiotics (e.g., erythromycin): may increase plasma concentration.

Moderate Interactions (Monitor Closely)

• CYP2D6 inhibitors (e.g., fluoxetine, paroxetine): may increase Quinagolide plasma levels.
• Antidepressants affecting serotonin (e.g., SSRIs): monitor for mood changes.
• Hormonal contraceptives: possible reduction in contraceptive efficacy.
• Diuretics: monitor electrolytes and blood pressure.