To compare the effects of using intrathecal prilocaine combined with fentanyl on duration of motor block versus that of intrathecal bupivacaine combined with fentanyl in elective caesarean section.

The participants in this study will be randomized into two groups based on computer generated numbers using online randomization program (research randomizer). Upon arrival to the operating room, patients will be monitored using electrocardiography, pulse oximetry, and non-invasive blood pressure monitor. The baseline values will be recorded .Heart rate and peripheral oxygen saturation (SpO2) will be monitored continuously; systolic, diastolic, and mean arterial pressure (MAP) will be measured noninvasively at 5 minutes interval during the procedure and during the PACU stay. An 18G-cannulae will be inserted, and pre-medication drugs will be delivered (metoclopramide 10mg). and 4-8 mL/ kg crystalloid infusion will be initiated . Nasal oxygen 3 L / min will be administered during the whole procedure.

• Group P: patients assigned to this group will receive intrathecal 50 mg (2.5 ml) of prilocaine 2% (Takipril, prilocaine hydrochloride 20 mg/mL, hyperbar, Sintetica) + 25 ug fentanyl (0.5 ml).
• Group B: patient assigned to this group will receive intrathecal 10 mg (2 ml) of bupivacaine 5% (sunnypivacaine hyperbaric bupivacaine 20 mg/4ml + 25 ug fentanyl (0.5 ml).

Inclusion Criteria:

• Age (18-35)
• ASA II
• Singleton, full term pregnant females.
• Height (1.60-1.90) m.
• BMI > 35 kg m-2
• Scheduled for elective caesarean section under spinal anesthesia.

Exclusion Criteria:

• Patients requiring general anaesthesia
• Known or suspected coagulopathy (international normalised ratio > 1.4), thrombocytopenia (platelet count < 100,000).
• Known peripheral neuropathy, neurological deficits or skeletal deformities.
• Known allergy to prilocaine, bupivacaine , fentanyl.
• Infection at site of injection.
• Patients' refusal to sign informed consent
• Patients with uncontrolled cardiac morbidities (patients with tight valvular lesion, impaired contractility with ejection fraction less than 50%, heart block and arrhythmias), hypertensive disorders of pregnancy, peripartum bleeding.