Norprolac (Quinagolide)

Quinagolide acts on the dopaminergic pathway to control excess prolactin production.

• Hyperprolactinemia: reduces serum prolactin concentrations, helping to resolve galactorrhea, restore normal menstrual cycles, and improve fertility.
• Prolactinoma: lowers prolactin output from pituitary adenomas, aiding in tumor size control and alleviation of associated visual or endocrine disturbances.
• Inhibition of lactation: suppresses milk synthesis and secretion, useful in conditions where lactation must be stopped for medical reasons.

• Quinagolide selectively stimulates dopamine D2 receptors in the anterior pituitary, mimicking endogenous dopamine’s inhibitory effect on prolactin release. By binding to these G‑protein‑coupled receptors, it reduces intracellular cyclic AMP and suppresses prolactin gene transcription, leading to decreased secretion of prolactin into the circulation. This pharmacodynamic action normalizes feedback loops within the hypothalamic‑pituitary axis and contributes to the therapeutic reduction of hyperprolactinemic states.

Quinagolide may be associated with a range of adverse reactions, varying in frequency and severity.

Common Side Effects

• Nausea: mild to moderate stomach upset that often resolves with continued therapy.
• Headache: transient tension‑type headaches reported by some patients.
• Dizziness: occasional light‑headedness, especially when standing quickly.
• Fatigue: general tiredness that may improve over time.

Serious or Rare Side Effects

• Valvular heart disease: potential fibrosis of cardiac valves requiring periodic echocardiographic monitoring.
• Psychosis: emergence of hallucinations or delusional thoughts, particularly in predisposed individuals.
• Severe hypotension: marked drop in blood pressure that can cause fainting or shock.

When prescribing Quinagolide, clinicians should consider several safety aspects.

• Renal impairment: adjust monitoring as quinagolide is excreted renally.
• Cardiovascular disease: evaluate for valvular heart disease before initiating therapy.
• Psychiatric disorders: monitor for emergence of psychotic symptoms during treatment.
• Pregnancy and lactation: use only if benefits outweigh risks, as safety is unknown.
• Drug interactions: review concomitant medications that affect dopamine pathways.
• Store at ambient temperature: keep below 25 °C, in original packaging, protected from moisture and light.

Quinagolide can interact with other medicines; awareness of the interaction level helps guide clinical decisions.

Major Interactions (Avoid)

• Antipsychotics (e.g., haloperidol): may antagonize dopamine agonist effect, reducing efficacy.
• Ergot derivatives: combined use increases risk of vasospasm and peripheral ischemia.
• MAO inhibitors: potential for hypertensive crisis when used together.

Moderate Interactions (Monitor Closely)

• Antihypertensives: additive blood‑pressure‑lowering effect may require dose adjustment.
• SSRIs: may increase the incidence of nausea and dizziness.
• CYP450 inhibitors/inducers: can alter quinagolide plasma concentrations, necessitating therapeutic monitoring.