Intravenous neostigmine was recently reported as an effective treatment for PDPH for parturients after intrathecal (IT) block which is postulated to be through its central effects on CSF secretion and cerebral vascular tone modulation. Intrathecal neostigmine has been investigated widely and found to be an effective adjuvant to bupivacaine for postoperative analgesia.

The objective of the current study is to investigate the possible prophylactic role of intrathecal neostigmine as an adjuvant to bupivacaine in reducing the incidence and severity of post-dural puncture headache in parturients scheduled for an elective cesarean section.

Upon arrival to the operating room standard monitors will be applied and continued all over the operation, an 18G peripheral intravenous (IV) cannula will be inserted, and 15 ml/kg of Ringer lactate solution will be infused.

The intrathecal block will be performed via a midline approach into the L3-4 or L4-5 interspaces in a sitting position under strict aseptic condition using a 25-gauge spinal needle after administration of 3 ml of lidocaine 2% (60 mg) as a subcutaneous infiltration, a 2.5 ml of hyperbaric bupivacaine, 0.5 % (12.5 mg) in addition to the content of the prepared study syringe will be mixed and slowly injected.

After ensuring sufficient anesthesia level by loss of sensation to pinprick at the T4 level, the surgical procedure will start with continuous hemodynamic monitoring and recording.

At the end of the surgery, the parturient will be transferred to the postoperative anesthesia care unit (PACU).

Parturients will be transferred to the obstetrics ward after fulfilling the criteria of the modified Aldrete scoring system ≥9.

The participants who will be diagnosed to have PDPH Per the previously mentioned criteria will be treated by using oral Panadol extra™ (paracetamol 1gm + caffeine 135 mg) (Manufactured by: Alexandria company for pharmaceuticals & chemical industries under license: GlaxoSmithKline Consumer Healthcare Ltd. Ireland) at 6-hour interval in addition to ensuring good oral or intravenous hydration (2-3 L/day) and bed rest. Severe Intractable headache (VAS ≥ 4) persistent for more than 48 hours with no response to conservative measures will be managed with an autologous epidural blood patch after participant approval and consent signing.

Assessment of the quality of the sensory and motor block in terms of the onset and duration will be done at 2 minutes intervals during the first 10 minutes after giving the spinal block, then at 10 minutes intervals until the end of the surgery, and at 15 minutes intervals while being in the PACU.

Inclusion Criteria:

• American society association (ASA) physical status class II parturients with a single fetus who will be scheduled for an elective caesarian section by Intrathecal block.

Exclusion Criteria:

• Body mass index more than or equal to 35 kg/m2.
• Any contraindication to Intrathecal blocks such as local infection, bleeding disorders, or parturient refusal.
• Allergy to neostigmine or other drugs will be used in the study.
• Long-term opioid use.
• A history of chronic pain, migraine, cluster headache.
• Digestive problems with nausea and vomiting; cognitive dysfunction or memory disorders.
• Significant renal, hepatic, and cardiovascular diseases.
• History of urinary retention or bronchial asthma.
• Inadequate or failed Intrathecal block.
• Complicated pregnancy such as hypertensive disorders of the pregnancy, abnormal placenta, or uterine atony.